Mine is a 2011 that was bought new, that has been owned just shy of 3 years. It has 21,000 miles on it. It was the exact model, floor plan and chassis I wanted, and got it for a good price too.
My game plan is to own it for at least 10-12 years and 75-80k miles. The way things are going, I may keep it a few years more than that until I retire, and buy the next and final RV at that point for the next 12-15 years.
It does come down to chassis and house maintenance, along with frequent use. Example: I check and recaulk windows and seams twice a year at the beginning and end of camping season.