This is so interesting! I've always been very big on getting a lot of sleep and could never ever pull an all-nighter, but for those times when you just have to go through with it I used to get up really early (like 3) and study.
Well I'm 21 now and suddenly I can't wake up anymore! However to submit my project thesis on time I've been sleeping at 4 or 5am every night for several nights in a row this week, and magically, I can do it without a problem!
All you people not able to stay up at night, try waking up early now, haha.