Good question - it would be interesting to know what the oldest one on the forum is!
Really I believe if you didn't get a lemon and have issues in the first couple of years, you get out of them what you put in them. No reason they couldn't last 50+ years if you keep up on the maintenance and repairs and are willing to replace a few larger items as they break down over the years (ie, fridge, trailer seals, etc).
2015 Starcraft 26BHS
2014 GMC Sierra 1500 SLT