Some pretty good answers so far,it seems to me that the quality has gone down in the last several years.
So older ones have a lot better quality,my 2006 Tioga has not given me any problems as far as the quality of the build,All doors, cabinets and drawers are tight and working as they should, the fit and finish is still very good. Even all the tank sensors work!
Things to look for is not only quality of the build when looking for a used unit but also the maintenance that was given the unit.
Another avenue to look at is the
Rental Market there you have a quality build that has to stand up to vigorous use and is maintained well to keep in on the road and making money.
There is more than 140 Forum members here that have chosen to do that and are happy with their choice.