IMHO, it all depends on the INITIAL quality of the coach. Well build motor homes will tend to hold up better than the mass produced units. I've seen some beautiful early 90's Liberty coaches and Blue Birds that would put the newer paper-bag buses to shame. I would certainly pick a 15 yo Newmar over a 7 yo Thor.
The issue with buying an older coach is mostly in the appliances; fridge, water heater, furnace, A/C units, genny etc. All of these are fixable/repairable with parts readily available until you get to the 25 year mark. Then it becomes hit or miss. Example; I wanted to replace the seals on the fridge doors. Seals not available, need to replace door. Doors only available from salvage lots, seals probably in worse shape than the ones I have. Solution - weather striping.
Another issue is simplicity. Numerous slides or large slides, self leveling systems, hydro hot heating, all electric coaches all add complexity along with convenience. More stuff to break.
Rig in sig is now 22 years old and still going strong. Original fridge, genny, furnace and A/C units. I spend about $5k a year in maintenance and upgrades.
