Applying socioemotional selectivity theory to the domain of health, we examined the interplay of social-cognitive predictors of physical exercise in two groups of people who perceived their remaining lifetime as either expansive or limited (based on subjective longevity ratings). Individuals (N = 370) who were prescribed physical exercise were assessed at discharge from orthopedic rehabilitation as well as 6 and 12 months later. Multigroup structural equation modeling showed differences in latent means, interrelations of predictors, and amount of explained variance. Individuals who perceived their time as limited reported a less favorable profile on social-cognitive variables and less exercise goal attainment. We give first insights on how health self-regulation differs in these groups, and we discuss avenues for intervention based on socioemotional selectivity theory. In contrast to chronological age, subjective life expectancy can be targeted by intervention.