It depends. I'm a full-time employee, a full-time student, I'm in a band that practices twice a week and plays a show every other week, and I'm in the Air National Guard. Outside of my fiance, the gym is the other of thing that I have time for during the semester. It works fine as long as I keep my priorities straight. Unfortunately, my gym works are usually cut short with the expectation to weekend I don't work. Usually it's an hour for the time I enter until the time I leave.
I'd always like to be there for 1.5-2 hours to ensure cardio and a long sit in the suana afterwards (not included in the time).