My thoughts on sleep:
I think that everyone has different circadian rhythms. (In case you didn't know, "circadian" comes from Latin words meaning "about a day" and describes the body's internal mechanisms that regulate your daily functions like sleeping, waking, hunger, etc.) The Earth's natural daily cycle is about 24 hours. However, most people's natural cycles don't correspond exactly to the Earth's rotation. This can lead to problems with sleep.
For example, since about 1995, my body has been on about a 22 hour cycle. If left to follow my body's natural urges, I will sleep for about six hours, wake up, and get tired again 16 hours later. This means that I tend to get sleepy earlier and earlier each night. Much to the annoyance of my wife, whose own daily cycle is about 26 hours long. She prefers 8-9 hours of sleep, and doesn't get tired again for about 18 hours.
This explains a lot about the "morning people" and "night people" differences. If your body's cycle is less than 24 hours, you will be a morning person. If it's more than 24 hours, you'll be a night person.
The length of your circadian cycle can change, too. Before 1995 I was a world-champion night owl, and used to hate to get up without at least eight hours of sleep. I have no idea what made my cycle change. It wasn't a conscious decision, and I can't identify anything that might have triggered it. I just gradually noticed that instead of sleeping late, I was just staying in bed awake for a few hours each morning, so I decided to get up and do stuff instead.
Of course, no one is a slave to their sleep cycle, otherwise I'd wind up falling asleep at noon and waking up at 6PM (which I have done when I worked graveyard shift jobs, but that was before I got onto my current cycle). If I stay up late on weekend nights, that can reset my sleep schedule so that I don't wind up going to bed any earlier than 9PM on the weeknights. A good game of Civ does a great job of making me forget when my body is telling me to sleep. (-:
One other random thought: I've never understood the people who see sleep as a waste of time. I've always considered sleep to be natural and healthy. I understand feeling like there isn't enough time in the day, but to me, the big waste of time is work. It has always annoyed me that I have to spend one-third to one-half my waking hours doing stuff I'd rather not be doing just to assure that my material needs are met.
I can't sleep a wink. Every night.
Heck, that may make it worse....
[dance]
