For me, it's usually about 6-7. If I get less than 6 for a couple days in a row, I'm not at my best, and in fact get negative and unproductive. More than 8 in 1 night, and I wake up with a bad headache like I never slept at all. I always wake up at 5:30, no matter what time I went to bed, and I don't have an alarm clock. I hate that, because I know I can't stay up to go out with my wife, or anything, if I'm going to need to do anything important the next day. I just can't sleep past that time, even if I want to. I don't start workout until 9, and my job is here at home, so there's no need to be up that early. I use it to eat breakfast, horse around here on the internet, or do housework, whatever. So I go to bed at 10:30 or 11 every night, and sleep great.
Charles