The rapid increase in human life expectancy during the last decades sees many individuals confronted with the prospect of living a very long life. Whereas advances in life expectancy are often being celebrated in scientific communities, it is still largely unclear to what extent individuals embrace the prospect of a long life and wish to reach a very old age. To address this issue, the present dissertation focuses on the construct of ideal life expectancy, which can be defined as a personal desire regarding the length of one’s life. Understanding personal ideal life expectancies, and the antecedents, processes, and consequences surrounding them, is particularly important when assuming that individuals’ beliefs, choices, and behavior can affect their aging process and actual length of life. Within the general introduction of this dissertation (see Chapter 1), the construct of ideal life expectancy is embedded in the theoretical frameworks of self-discrepancy theory and the psychology of life-longings. With this, it is highlighted that individual ideal life expectancies constitute self-related ideals, which can and often do diverge from perceptions of reality (i.e., perceived life expectancies). Indeed, many individuals seem to wish for a life longer than the one they anticipate, express a certain dissatisfaction with the length of their life, and experience a phenomenon we have labeled as subjective life expectancy discordance (i.e., the discordance between ideal and perceived life expect-ancy). In all this, ideal life expectancy is however a construct with considerable interindividual differences and it is scarcely understood why some individuals consider their perceived life expectancy ideal, whereas others would opt for rather short or unrealistically long lives. The central research questions of this dissertation focus on the contexts and experiences (i.e., culture, age, health, and the coronavirus pandemic) as well as personal belief systems and mindsets regarding living, aging, and death that can determine individual ideal life expectancies. Furthermore, it is addressed how processes of anticipation, evaluation, and contrasting likely surround the immediate formation of ideal life expectancies. When forming their ideal life expectancy, individuals need to rely on more general anticipations of their personal life in old age as well as the specific anticipation of perceived life expectancy. Individuals can then evaluate those anticipations as (un-)desirable, (un-)acceptable, or even threatening (cf. aging-related fears) and can be encouraged or discouraged to wish for a certain life expectancy. Consequently, individuals are free to actively decide on an ideal life expectancy that is in concordance and acceptance of their anticipations, or in discordance and in contrast to their anticipations. Here, it is studied how certain aging-related fears as well as general anticipations of the future relate to ideal life expectancies. Lastly, affective and behavioral consequences of individual ideal life expectancies are investigated. Particularly, it is assumed that (strong) discordances between perceived and ideal life expectancies can stimulate health behavior change, but also negatively affect psychological well-being and foster experiences of dissatisfaction and despair. The specific research questions have resulted in four empirical research papers gathered in this cumulative dissertation. Paper #1 (see Chapter 2) summarizes prior research on longevity motivation and identifies three common belief systems and mindsets: The essentialist mindset idealizes an infinite life and aims at conquering or halting a biologically determined aging process. The medicalist mindset evaluates aging based on health and sees longevity as burdened only when pathology occurs. The stoicist mindset is a mindset of acceptance, which tolerates the challenges and vulnerabilities of the aging process as long as dignity and meaning can be preserved. The mindsets are then empirically explored in regard to the construct of ideal life expectancy. Results indicate that culture, self-rated health, and death acceptance act as potential determinants of ideal life expectancy. Additionally, the interplay of perceived and ideal life expectancy is able to predict health behavior change. Lastly, ideal life expectancy and its discordance to perceived life expectancy are established as stable and reliable constructs. Paper #2 (see Chapter 3) targets the relationship between ideal and perceived life expectancy more explicitly. Results indicate that average ideal life expectancies lie cleary above average perceived life expectancies and that most individuals would strive for a longer life than they anticipate. This experience of subjective life expectancy discordance seems to ease in old age, when ideal and perceived life expectancies become more concordant. In line with predictions of self-discrepancy theory, a stronger subjective life expectancy discordance was negatively related to different aspects of psychological well-being. Over the time span of two years, subjective life expectancy discordance predicted increases in negative affect. Additionally, subjective life expectancy discordance contributed to another form of subjective aging discordance: Individuals wishing to live longer than they anticipated to, also wished to be younger again than they perceived themselves to be. Thus, a discordance and dissatisfaction regarding the future aging process and length of life seemed to predict a discordance and dissatisfaction regarding the current aging process. Paper #3 (see Chapter 4) investigates a number of psychological constructs targeting the finitude of life (i.e., future time perspective with its three subcomponents future time opportunity, extension, and constraint, fear of death, and ideal life expectancy) in times of the coronavirus pandemic. Whereas the research indicates that future time perspectives decreased over the course of the pandemic and that fear of death peaked at its beginning, ideal life expectancies remained surprisingly stable throughout the pandemic. Ideal life expectancies thus seem to be shaped by more enduring contexts and experiences (e.g., health state and socioeconomic status) rather than momentary and transitory ones. Furthermore, it is explored how ideal life expectancy relates to the other psychological constructs of finitude: Next to the respective cross-sectional relations, higher ideal life expectancy seemed predictive of increases in future time opportunity, future time extension, and fear of death, leading up to the topic of the fourth publication. Paper #4 (see Chapter 5) focuses on the role of aging-related fears for individual ideal life expectancies. Following predictions of terror management theory, it is assumed that a strong fear of death is related to pushing death into the more distant future and wishing for a longer life. In contrast, fears regarding the aging process, such as the fear of loneliness in old age and the fear of aging-related diseases could color anticipations of aging in such negative and threatening ways that individuals may prefer to avoid those by wishing for a shorter life. Results indicate that differentiations mainly occur in regard to whether individuals would like to reach a very old age. Indeed, a stronger fear of death was related to higher ideal life expectancies and the wish to reach a very old age across two studies. Additionally, individuals fearing loneliness in old age or aging-related diseases while being unafraid of death, wished for particularly short lives. Explicitly negative anticipations of the aging process such as aging-related fears can thus partly explain why individuals wish for longer or shorter lives. In the general discussion (see Chapter 6), the findings of the four research papers are summarized and synthesized. In regard to contexts and experiences, aspects of an individual’s biography such as culture, gender, age, socioeconomic status, and health state seemed decisive for individual ideal life expectancies. In contrast, ideal life expectancies seem rather unaffected by temporary contexts such as the coronavirus pandemic. Three overarching belief systems and mindsets for longevity motivation were identified. Additionally, individuals’ views on death (i.e., fear of death and death acceptance) were associated with ideal life expectancies. Regarding the more immediate formation of ideal life expectancies, reciprocal processes between anticipations of the own aging process and future (e.g., future time perspective) and personal ideal life expectancies can be assumed. Research furthermore supports the assumption that individuals actively differentiate between the more rational anticipation that is perceived life expectancy and the personal desire that is ideal life expectancy. Whereas most individuals wish to live longer than they anticipate, particularly older adults also experience concordance between their ideal and perceived life expectancy. The general discussion also highlights and discusses the finding that a subgroup of individuals wishes to live less long than they anticipate to. Lastly, next to ideal life expectancy’s impact on health behaviors and psychological well-being, there seem to be cognitive consequences in regard to states of acceptance, the envisioning of the future, and potentially, active goal-setting and intention-building. The discussion concludes in an expanded research model and highlights social contexts and relationships, aspects of subjective aging, and the end of life as potential areas for future research surrounding ideal life expectancy. The main implications of this dissertation refer to the reliability and stability of the construct of ideal life expectancy, its embeddedness in the research on self-related ideals and the research on subjective aging, and the more far-reaching content of the identified mindsets of longevity motivation. On a practical level, individual and average ideal life expectancies could affect research questions, medical treatment and decision making, as well as societal views on old and very old individuals. Due to relations to negative psychological well-being and fear of death, the constructs of ideal life expectancy and subjective life expectancy discordance may furthermore be of importance for overall psychopathology. Most importantly, however, this dissertation is able to show that many individuals indeed appreciate the prospect of a long life—a finding that could be utilized to foster a positive but realistic approach to living into very old age.