The only time I ever had an all-nighter was when we had classes one day in a row (so basically 24 hours of classes, which was kind of a tradition at our school). The classes from 2 AM to 7 AM were pretty lax for obvious reasons, and we had a great time even though many of us could hardly stay awake the following day. xD

I still regret that I didn't take the all-nighter "history of rock&roll" class when I had the chance, though.