The relationship between job satisfaction and time is a fundamental question in organizational behavior. Yet given inconsistent results in the literature, the nature of this relationship has remained unresolved. Scholars’ understanding of this relationship has been limited because studies have generally not simultaneously considered the two primary time metrics in job satisfaction research—age and tenure—and have instead relied on cross-sectional research designs. In this study, we develop and test an empirical model to provide a more definitive answer to the question of how age and tenure relate to job satisfaction. Our analyses draw on longitudinal data from 21,670 participants spanning a total of 34 waves of data collection across 40 years in two nationally representative samples. Multilevel analyses indicate that people became less satisfied as their tenure within a given organization increased, yet as people aged—and transitioned from organization to organization—their satisfaction increased. We also found that job rewards, as exemplified by pay, mediated these relationships. We discuss empirical, theoretical, and practical implications of our findings.