Can 'O Worms: how long can I expect my 5er to last?

They’ll generally last as long as the care put into them.
Seeing as I’ve never seen a relatively new camper like either of yours with leaning walls, I’ll say you must ride em hard and put ‘em up wet.
Pull it until it don’t pull no more if you just let them rot away, anyways.
Be a waste of money to start decreasing the life on a new one until this one is completely used up, based on your track record.