Not unusual, around here, to see CarriLite fivers from the 1980s, and Hitchhikers from the late Pre-fiberglass era to the present. Partly because they were sales leaders for premium and full-timing market, but still not representative of high volume models.
A lot depends on how it is used, or how it is stored if it is not used. If well used, usually also maintained. If sitting for 20-30 years, big difference between climate controlled storage vs in a barn vs out in a field.
I was thinking 10 years is a long time, but looking at mine as it passes that mark, looks like another 10-20 years is going to be easy, unless it gets to where critical high tech chassis parts (like the ECM or some sensors) are no longer available.