It depends on how many hot babes are around and what kind of music they are playing.

Seriously, I think Mike and Primo said it best. When you reach a certain level of understanding your body you can really on judgement and instinct. For example I need more rest between sets of legs than I do for bi's or tri's. Because most leg exercises incorporate not only the largest muscles in the body but a large group working at one time, your body uses much more oxygen and therefore needs a little more time to recover before the next set. So I guess I'm saying that the length of time in the gym also depends on what I'm training.

P