To examine whether the validity of perception-based intensity regulation would be affected by exercise duration, 20 subjects were recruited to complete a maximal exercise test (GXT) and four submaximal trials of varying duration and intensity using a cyle ergometer. During GXT, ratings of perceived exertion (RPE), oxygen uptake (VO₂), heart rate (HR), and power output (PO) equivalent to 50 and 75% VO_2peak were determined. During each trial, subjects were to produce and maintain a workload using RPE estimated at 50 or 75% VO_2peak for 20 or 40 min, and VO₂, HR, and PO were measured throughout the exercise. No differences in average VO₂ were found between the estimation and production trial of either duration. However, average HR and PO were lower (P < 0.05) during the production trial of both durations. It appears that exercise duration has a minimal impact upon the accuracy of using RPE to regulate a target metabolic demand.