Another one of those totally "dependant" questions....
It all depends on where I hunt and what I'm hunting for. The three big bear stands that we build in the trees were 20'-25' because we wanted to be up above them so small movements in the stand didn't give us away. I will usually go about the same when I hunt from my climber. Again I want to be out of their line of sight. Too high and you don't have a good double lung shot. I might not go so far up if the tree has a lot of low branches. I like to use the surrounding branches for cover as well. I have roped them and pulled them close for additional natural cover. It also depends on the terrain around me. I hunt in the mountains so I might have to go higher to get a good angle for a shot. I don't like to go too high because the tree gets smaller and the stand starts to lean forward. I didn't set my stand up correct one time and it leaned forward. I had to literally hold on so as to not to fall off.

On that note....always get down to ground level to change the straps on your stand. I was about three or four feet off when I realized I didn't have the base angled up enough. I redid the top and tried to pick the bottom up with my feet and disconnect the strap...which I did...and then the stand slipped off my feet....whoosh to the ground. It is also a good idea to have staps between the two sections..to prevent this.

Reid