My neighbor has a '73 Nomad TT that has never leaked. Sure its dated and colors are a bit faded. He bought it from the original owner who had a trailer shed (one end of a open hay barn).
Our first 5er was a 2 month old 26' 1984 Aljo by Skyline. Sold it to neighbors friends in '91'ish. I see it a couple of times a year and it still looks like a 1984 RV.
Our current 5er is a '97 model and looks like it did the first day we bought it.
Our last stay was in Branson, MO. The guy at the counter asked for the trailers date. He looked out the window and commented it looks new. All of my RV's were kept in the tractor shed of the trailer shed out of the sun.
I do my own twice a year check up on the roof and exterior and all maintenance.
Neglect them and they don't last long.