All other things being about equal.... is a person better off buying (for example) 1) a 8 yr old Class B with 60,000 miles or 2) a 12 yr old class B with 30,000 miles
I would prefer to not buy anything more than 5 years old. Why? Because I'd be keeping it for at least 10 years and perhaps 15 years. That means it would be 20 years old when I was done with it.
Plastic depalmerizes over time. It becomes fragile.