How old is too old, subjective question but I want opinions

Compared to my 1991, you have a relatively new unit. We've had ours since new and don't hesitate to go coast to coast in it. As far as replacing a tranny or engine, that expense would be less than the depreciation hit the first day you drive another new one off the lot. I am afraid if I upgraded, I would be a two motorhome owner since I don't think I could part with mine.