While we know about lay attitudes towards death and dying, we understand little about the ways people estimate their overall personal risk of life-limiting disease and/or death. This study contributes to the limited literature on lay longevity reckonings, with a particular focus on how these reckonings may influence health behaviours. Semi-structured interviews were held with 21 young older adults (54-65 years), addressing the core questions of 'What do you think you will die from, and how long do you expect to live?' Participants indicated their longevity estimation was guided by three key frameworks: family history, environment and lifestyle factors and lived experience. The reckoning process was also moderated by assumptions about loci of control and self-efficacy and the information available to participants. A tripartite model of death risk assessment is proposed, extending the idea of 'negotiated risk' beyond the scope of family history where it has received most attention. We argue that by drawing on the three risk-assessment frameworks, determining patients' predisposition for external/internal attributions of control and perceptions of self-efficacy, clinicians will be better equipped to understand - and thus guide - patients' reckonings of longevity and health behaviours that are influenced by it.