Our 38ft 5th wheel was purchased new in 1994. It was primarily used for long weekend trips (3 to 4 days) once per month with a 2 to 3 week stay during the summer each year. This was for the first 15 years. For the past 10 years the summer stay has increased to 3 months with the occasional long weekend trip.
When not in use, the trailer is stored outdoors uncovered in Southern California about 6 miles from the ocean.
The edpm roof needs to be replaced and over the years I have replaced typical wear and tear items (batteries, tires, brakes and the awning fabric) we did have to replace the refrigerator coil at 10 years.
Three years ago one of the springs broke and I replaced all 4 springs and equalizers.
I do preventative maintenance which I believe has contributed to the long life. The trailer is solid and still looks new when it's washed and waxed. The interior is near showroom condition.
With proper care the RVs last. Our previous TT was 16 years old when we sold it to buy the 5th wheel.