Wear and tear is usually determined by what you used to seal them. If you used something like Modge Podge standard, which isn't water proof, then you'll need to reseal them eventually. Same goes for UV exposure...some sealers will yellow after awhile.
My own rock structures have held up very well after a little more then 2yrs. I've only had to reseal the one of the structures in my females viv (she's messy).