It's (presumably) paid for, (presumably) in good condition, and (presumably) meets your needs and wants pretty well. I'm siding with everyone else and saying you should enjoy it to the fullest. An RV (or truck) is not generally an investment, financially speaking; they lose value over time, rather than appreciate.
I don't think you could end up money ahead to buy a new truck and a new fifth wheel, certainly not after another few years when they have depreciated substantially. You would get greater shininess for awhile, but IMHO that's about all. For most vehicles, the early part of their life is the worst for depreciation.