During weekdays and Saturday I sleep about 6 hours. That way, when I wake up, I wake up during the light sleep stage which allows me to quickly wake up and still feel rested. However, on Sunday I try to sleep for 8 - 10 hours so I get the REM sleep my body requires.
I don't sleep very long - usually 4 or 5 hours - but for some reason - the more I sleep - the more tired I am - so If I sleep 8 or 9 hours - I can't function LOL