I usually sit about 3-4 hours, but have sat most of the day also, (with a break sometime during the day).
If possible I much prefer setting up the stand prior to actually hunting in it. Some water, something to stifle coughing are almost always with me.
Make sure you pick the right tree! A few years ago I walked in to an oak tree that I had pre-selected for a morning hunt ( in the dark). It had a perfect position for a trail that crossed a barb wire fence, good for a predominantly NNW wind.
I walked in before light, put a scent attractor in a sapling, and put my stand up in the tree. As the dawn started lightening up the woods, I realized I was in the wrong tree.
Then the dilemma. Do I stay put or move back up the fenceline 50 yards or so? I had a lot of confidence in the other location so I decided to chance making the noise that I knew I would.
One problem, after making the move and climbing up into the tree, I realized I had left the attractor in the sapling on the other side of the first stand. But, feeling I had already done too much fooling around I decided to leave it.
About an hour later I could just barely make out the nose and the antler tips of a very large buck about an inch away from the sapling, smelling the scent left there.
Never, never, never sit in a treestand with out safety belt. A friend of mine fell out of his and was saved because as he was crawling out to the road across a CRP field(with a broken leg and other serious injuries) a guy driving by saw his hat moving just above the weeds.
But having warned you, there is something about sitting in a properly placed treestand on a beautiful fall day that I thoroughly enjoy. Have fun with it.