We are going on thirteen years with our diesel pusher and it still looks like new and running great at 61K miles. We plan to keep it for several more years since it has been a pretty good coach.
But I think any coach will last you a long time if you take care of it. Change the oil and filters at regular intervals. Lube the chassis as per manual instructions. Lube seals on the slides on a regular basis. Keep your furniture clean and apply the proper leather cleaners as recommended. Wax the coach at least once a year to preserve your paint job.