Tony B wrote:
I know that maintenance and general care means a lot, but generally, at what age do they become more problematic than what they are worth?
There is no set time or duration. It's just like with the family car. Once they start nickle-and-diming you beyond your comfort level, you begin to think about selling or trading. Same is true with an RV. Everyone has a different threshold level. Sometimes folks are ready to sell after 3 days, others after 33 years.
The best you can do with a used unit is to inspect for everything. Crawl under the unit on your back and see what's under there, to crawling around on the roof to see what's "up" there. Then inside and outside, every nook and cranny, every appliance, all systems. Everything! Then make your decision when you detect a deficiency if you can fix it, live with it as is, or if it's too much for you, then leave it and move to a different unit.