I've encountered dozens of treestands in the public lands during post-season scouting. The farther back into security cover I've gone, the fewer stands I see, but some people hunting in CT leave stands on public land year round even though the regs require you to remove them after the season ends. I also frequently see DIY 2x4 stands, screw in steps and bow hangers, etc., that are in violation of the regs:
"The construction or placement of permanent tree stands involving damage to any tree or shrub is prohibited. The use of portable tree stands (climber, ladder, or hang-on) is permissible. However, all tree stands must be removed from state properties at the conclusion of the hunting season."
Despite the fact that they're breaking the law by leaving the stands in the woods, I personally don't touch the stuff if it's not mine. I have heard of more than one instance near me where someone had well hidden trail cameras and knew who messed with their tree stand setup ... then sabotaged the person who messed with their stuff later.
If I *really* liked the spot, I have setup right next to it, but only if no other hunter was there that day. But more and more I try to stay away from other hunters entirely.
The problem with hunting a spot that someone else is hunting is that you never know when they're coming and going unless you put out your own well-hidden cellular trail cams. And if they're not as good of a hunter as you are, they might be disturbing deer and stinking up the place with human scent while you're not there. That's just one of the realities of hunting public land and a good reason to find other places way back and difficult to access that have good deer sign but otherwise appear unhunted & undisturbed.