Well I actually have noticed people's sleep patterns for years. I actually get up at 6:30 every day - mainly because I have to, but I can stay awake all day and be as active as anything, and there is still no way my body will sleep at that time. In fact, if I get more than 7 hours, I get a headache and feel like I've underslept. Then there are other people who simply can't get less than 8 hours or they feel it and whom naps are no problem. With me, naps leave me feeling like the gumpiest, tiredest person alive.
I actually prefer to follow what I read a long time ago, which is to sleep for short periods, but twice a day - not always possible. But one period of 4 hours, followed by another 2-3 later.