Anything over 7-8 hours makes me sleepy, 5 hours is JUST RIGHT...now if i work out, it's still the same. I remember when i worked during the day time, if I went to sleep at 11:30pm-12:00am, after several days of having my alarm set to 5am, I automatically woke up at that hour---went out and jogged, and was ready for the day.
Sleep is the cousin to Death