Good points Mile High. I agree no matter what the condition interiors become dated and technology keeps evolving. Nevertheless after 10 years I feel I have won the depreciation value and got most of my money out of the unit.
I know no one truly wins the depreciation battle,but after 10 years I'm less concerned with the units resale value.
The key is to keep up on the maintenance even if the unit is stating to get old and worn. A garage really helps keep the unit in like new condition,but as you point out it may not be as cost effective as one would hope.
I do believe there is a point of no return. One can hold on to a RV a little too long to the point it has little value to anyone else.