ORIGINAL: Danny45
The belts themselves should be fine. They resist moisture, mold, and mildew really well. I'd be a little concerned about their metal attachment points though. If I were you, I'd yank them down and inspect them really good before climbing into a tree with them. Screws and bolts are usually steel, not aluminum.
Your kidding right? Are you saying that you think the bolts will fail before the straps will? Can't say I've ever seen a bolt get chewed on by a squirrel. I'd check the straps wayyyy before I'd worry about the bolts.
My opinion is if your going to leave them up, at the very least check the straps before setting foot back in it. Also if you have it attached to a fast growing tree, the strap may be stressed from tightening up over time.