It's actually variable- the 15s go quickly, because I'm doing only one set. The sessions get longer as I get into the 10s and especially the 5s, as I add sets and concomitant rest periods. The 15s take about 20-25 minutes, while the 5/negs take up to an hour. It also depends on how many lifts I'm doing, of course! Some cycles I do only compounds, and others I add in isos.