during the week i usually sit at one table for about 3 hours or less a night. I skip some nights, like Thursday I don't play at all cause I work late and most times I won't play on Friday's cause the club down the street from me has a live tourny every Friday night so I'll play there. On the weekend I'll put in a good 5 hours Sat morning and Sunday morning.
During this time I typically get up every hour or so when the blinds come around and sit out for about 15 minutes while I'll grab something to eat, walk around, entertain the kid, yada yada....
I've actually found that if I play straight through for 3 hours I will start to play very loose and tend to make calls I wouldn't normally.