Although experts recommend regularly reassessing adolescents’ risk for violence, it is unclear whether reassessment improves predictions. Thus, in this prospective study, the authors tested 3 hypotheses as to why reassessment might improve predictions, namely the shelf-life, dynamic change, and familiarity hypotheses. Research assistants (RAs) rated youth on the Structured Assessment of Violence Risk in Youth (SAVRY) and the Youth Level of Service/Case Management Inventory (YLS/CMI) every 3 months over a 1-year period, conducting 624 risk assessments with 156 youth on probation. The authors then examined charges for violence and any offense over a 2-year follow-up period, and youths’ self-reports of reoffending. Contrary to the shelf-life hypothesis, predictions did not decline or expire over time. Instead, time-dependent area under the curve scores remained consistent across the follow-up period. Contrary to the dynamic change hypothesis, changes in youth’s risk total scores, compared to what is average for that youth, did not predict changes in reoffending. Finally, contrary to the familiarity hypothesis, reassessments were no more predictive than initial assessments, despite RAs’ increased familiarity with youth. Before drawing conclusions, researchers should evaluate the extent to which youth receiving the usual probation services show meaningful short-term changes in risk and, if so, whether risk assessment tools are sensitive to these changes.