This study assesses self‐control theory's stability postulate. We advance research on self‐control stability in three ways. First, we extend the study of stability beyond high school, estimating GBTMs of self‐control from ages 10 to 25. Second, drawing on advances in developmental psychology and social neuroscience, especially the dual systems model of risk taking, we investigate whether two distinct personality traits—impulsivity and sensation seeking—often conflated in measures of self‐control, exhibit divergent developmental patterns. Finding that they do, we estimate multitrajectory models to identify latent classes of co‐occurring developmental patterns. We supplement GBTM stability analyses with hierarchical linear models and reliable variance estimates. Lastly, using fixed effects models, we explore whether the observed within‐individual changes are associated with changes in crime net of overall age trends. These ideas are tested using five waves of data from the Family and Community Health Study. Results suggest that self‐control is unstable, that distinct patterns of development exist for impulsivity and sensation seeking, and that these changes are uniquely consequential for crime. We conclude by comparing our findings with extant research and discussing the implications for self‐control theory.