This study examined the regulation of out-of-class time invested in the academic activities associated with a physics class for 20 consecutive semesters. The academic activities of 1676 students were included in the study. Students reported investing a semester average of 6.5 ± 2.9 h out of class per week. During weeks not containing an examination, a total of 4.3 2.1 h was reported which was divided between 2.5 ± 1.2 h working homework and 1.8 ± 1.4 h reading. Students reported spending 7.6 ± 4.8 h preparing for each in-semester examination. Students showed a significant correlation between the change in time invested in examination preparation (r = -0.12,p < 0.0001) and their score on the previous examination. The correlation increased as the data were averaged over semester (r = -0.70, p = 0.0006) and academic year (r = -0.82, p = 0.0039). While significant, the overall correlation indicates a small effect size and implies that an increase of 1 standard deviation of test score (18%) was related to a decrease of 0.12 standard deviations or 0.9 h of study time. Students also modified their time invested in reading as the length of the textbook changed; however, this modification was not proportional to the size of the change in textbook length. Very little regulation of the time invested in homework was detected either in response to test grades or in response to changes in the length of homework assignments. Patterns of regulation were different for higher performing students than for lower performing students with students receiving a course grade of "C" or "D" demonstrating little change in examination preparation time in response to lower examination grades. This study suggests that homework preparation time is a fixed variable while examination preparation time and reading time are weakly mutable variables.