I find for me it's psychological. I can get 6 hours of sleep and feel fine the next day if I'm doing something that's interesting and fun and keeps me awake. If I'm sitting at a desk in a cubicle then I'm tired as fawk. Maybe that's the only difference between young and old is that life is more fun when you're young. Although it was the same when I was in high school I was always so damn tired at school cause I'd stay up till 1-2 am. :dunno: