With very few exceptions, RVs are highly depreciative assets. Therefore, it is hard to make comparisons between stick houses and RVs, unless you let the stick house rot to the ground. Travel needs tend to dictate whether you buy and keep, or trade regularly.
With only 60k miles on your rig, it will probably run another 40-60k with few major issues. IF you are "week-end warriors" and dont put on a lot miles, and your uprades keeps the tribe happy, then keep the current rig--but realize it will have little wholesale value by the time you have it paid off--improvements and remaining monthly payments are down the drain.
However, it sounds like the size and layout are nolonger meeting all of your travel needs, plus, if you ever decide to drive more miles, repairs will eventually increase. Unless you are independently wealth and can "afford" new every few years, it seems like the best plan is to shop for RVs with involved owners and good documentation. "Try" to keep the residual valve close to the pay-off amount. Yes--it means continued monthly payments but if something happens and you need to sell, atleast you wont be shocked with a huge pay-off.
2003 40' MDTS
Garden Ridge, Texas