I max out at about four hours if I'm in a tree but, usually longer if I'm in a ground blind. During the rut usually longer; all day if the spot is hot with action.(nut)

Early Season - afternoons in stand by 4:00 - till dark.
By mid season begin hunting mornings also - in stand at gray light till 10:00 AM
November - in stand before light - sit till noon
PM sit 2:30 till dark - if rut dates coincide with a full moon - we enter at 7 or 8 AM and stay as long as possible - maybe even dark.

When I want to stay "in the woods" all day during mid season I will use a ground blind for the 10:00 AM to 2:00 Pm period - works best in southern river bottoms where deer are very active mid morning and mid afternoon - these are very well shaded areas that are really too dark after sunset. Also where we hunt the deer rut at this time in Mid October - which kicks activity up quite a bit.

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I can sit in the Lounge all day too. I know what 'ya mean about the giving thing, I'm 210. I just don't move in it too fast. The more of an angle, it seems to move less.

3-4 hrs in the morning and evening.  If things are hot I'll do all dayers, dark to dark.
Burnsie

4 hrs on average.  I read that just about every deer will move some every 4 hours, I just figure that if I am there for 4 hours I should see movement.  
If I am hunting alone, I will stay for 5 hours then get a snack and move to another spot for the remainder of the day, basically an all day hunt.

I don't hunt from a stand but, during the rut I'll spend the entire day, dawn 'til dusk in the woods. I've been known to sit under some low hanging branches and watch a trail for hours that showed signs of travel. I carry a little pack stool strapped to my pack and when I find a good spot, I'll pull it out and sit.

About an hour and a half, maybe two hours is all I care to fool with stationary hunting....I'm not a real patient man.  An exception to that would be if I'm bugleing or cow calling elk and I'm getting a good response. You fellas have probably had more success than me but I love to spot & stalk.  100% of my big game hunting has been in the Rocky Mtn West and most of that in Wyoming. To sit all day in one spot just seems silly from my perspective.  Can't do it.

All day if I have the time otherwise 6 hrs on average. My longest was the day I shot my first deer with trad gear. The wife dropped me off on state land at 5:30am and picked me up at 8:15pm.
My coldest sit was in -8 degree temps with 15 mph winds for 8 hrs. I pulled my longjohns up to my chest and tucked my arms in. Didn't see a single deer,LOL!
Last year was the 2nd coldest with 6 degrees for a high with wind chill included. I got in before light and at 3pm some doe came in. I was so cold that I could hardly draw my bow. My arrow fell off the rest and that was the end of that day.
Some day I'll either get the right clothes or have sense enough to get out of the cold. Being addicted to hunting has it's flaws,LOL!

If I'm on vacation and there are no obligations with the family or chores, I often to dark to dark.

If the leaves are crispy and I can rely on my ears to hear a deer come in, I sometimes take a book to pass the time.  Never had a deer sneak up on my yet under those conditions.

I have spent the entire day in my climber, not a lot of fun. I like popup blinds for the freedom of movement and selection of snacks for those long sits.

I miss my WT DEER!!!!  Im thinking hard about moving back to WI just for them, and just coming out for the month of September for elk.  Back on track learn your area!  I have spots in Wi that were a total bust to hunt in the morning, spots you could sneek in for a hour if i was running late.  I just try not to push deer around.  I guess what i'm saying is hunt as long and as much as you can.  (depends on how the land lays and so on.  Over hunting a stand is bad) If you have the time to sit all day during the rut, get after it.  I've seen some big boys between 12-3.  I've also shot some monsters by running out after work for an hour.  this kinda turned to a ramble, but what I'm saying is the longer the better, but by all means get out when you can (if it doesn't scare deer around.

I generally sit for 3-4 hours nowadays....though I must admit that I've been up a tree from dawn till dusk on more than one occasion. Mostly I sit the blind till late morning then I may move to another area and still hunt for a while and then go back to the stand in the afternoon

I try to stay 2-3 hours, I know I can stay alot longer if I'm seeing game. Even if its tukeys, tree rats or other critters, if I'm seeing activity I can saty alot longer.