In 1989 I built a treated wood swing set for my then 3yo and 1yo daughters. It was nailed together and bolted together in different spots. Two swings, a slide, and a set of rings for hanging and flipping. They used it almost every day that the weather was good. They outgrew it and I gave it away to good friends for their four kids. They have had it about ten years now. The plastic swings have been replaced as has the ring set. The treated wood is still holding strong after all the torque from the swinging, sliding, and flipping over the years.
If you build a treestand out of treated wood, build it well, check it regularly, then it'll last for years of weathered use and non-use. Even approved and inspected metal and cabled parts fail.
Just don't be reckless about it and you should be fine if you want to build one.
I trust my self-built wood tree stand more than my Gorilla climber.