Objective:To investigate the long-term effect of flexible duty-hour policies on resident outcomesBackground:The Flexibility in Duty Hour Requirements for Surgical Trainees trial showed no significant difference in overall resident well-being between flexible and standard duty-hour policies after 1 year. However, long-term exposure to flexibility could have adverse effects on duty-hour violations, resident satisfaction, and well-being.Methods:In 2014, 117 programs were randomized to flexible or standard duty-hour policy. Residents were surveyed annually following the American Board of Surgery In-Training Exam (∼3750 residents/yr; response rate 99%). Four-year trends within the flexible policy arm were analyzed using cluster-corrected Chi-squared tests. Differences between study arms were modeled using multivariable logistic regression.Results:Over time, there was a trend toward fewer 80-hour work week violations in the flexible arm (19.8%–17.0%, P = 0.06), and increased satisfaction with flexible duty-hours (91.9%–94.3%, P < 0.05). Although well-being decreased over time (85.1%–81.5%, P = 0.01), this was seen globally with no difference between study arms [odds ratio (OR) 0.96 (0.74–1.25)]. Likewise, at the end of the study period, there was no association between flexible policy and duty-hour violations [OR 1.25 (0.95–1.61)] or satisfaction with duty hours [OR 0.80 (0.55–1.19)] compared to standard policy. Residents in flexible duty-hour programs reported significantly fewer lapses in continuity than standard policy residents, until all programs transitioned to flexibility by 2018.Conclusion:Cumulative time under flexible duty-hour policies had no detrimental effects on duty-hour violations or resident well-being. After multiple years of flexibility, residents continue to report a high rate of satisfaction and positive effects on continuity of care.