We learned tons by going to the RV shows and a consignment lot (PPL in Texas). It was an eye opener to see new motorhomes at the shows with doors off the runners, showers a 6-foot person could not stan up in, and little piles of sawdust under the cabinets where they had been rubbing together.
If an RV can't last 2000 miles to go to a few shows, it will be a wreck in 30K miles.
At the consignment lot we saw what brands looked nearly new after 10 years (in our observation, the Foretravels and Bluebirds and the like), and which had body delamination, cabinets falling of the walls, electrical patches, etc. Appliances are pretty much the same in a price range, most chassis are pretty consistent. It is the body build that is so variable.
I have never been afraid of a bad appliance if the overall care of the coach looks good. You account for the defect in the purchase price and go get a new one.
Matt B