We have been in our present storage yard about 5 years and the rig next to us was new/barely used then and has not moved since. The fifth wheel hitch was clean and shiny black, not it is a rusty brown.
My SIL's stepdad had his fiver parked next our rig in the SIL's business lot for seven years. He did no maintenance on it and never moved it. When the SIL's Mom died, his stepdad decided to go to Minn. for the summer. The roof caulking had dried out and the interior had so much water damage he just gave it away.
Things happen and RV's get left to rust away.