I fall asleep around 2-3am every night and am up at 7:15am during the week. I'm 39. I've been a night owl since I was a teen, and even today I have to force myself to sleep. During vacations it becomes extreme, I easily stay up till 6-7am and sleep till 12 or so - which seems to be ideal as I always revert to those times given 3-4 days where I'm not required to be up early. Adjusting my schedule back to "normal" involves skipping sleep for a night.