10 years but I've seen "many" going to 15. These are restrictions , at very few parks and of those small number that do , it is mostly on monthly or greater stays. In many states that gives " rights " to the renter making it difficult for them to evict problem tenants.
Except for the exclusive and very expensive "resorts" exceptions are made for meeting appearance standards .
We have a 13 , almost 14 year old high end coach that still looks new. I have never been stopped.