I changed one on an old work truck. It was about 15 years old and still cooled but not good. I helped a friend change one that acted the same way on a 6 year old camper. Both probably went bad from sitting long periods, maybe years without use and both probably could have lasted much longer with more frequent use. Ive added a second unit in my old 5th wheel and I also added an ac to an enclosed trailer that didn’t have one. I have had to change two fan motors and one fan assembly in AC units. In my 14 history running these AC units, I’d say they are pretty tough. They are sealed so usually they don’t leak and I think that using them is better than letting them sit for long periods. I haven’t had many other major issues other than the power control board went bad in my old refer, water inlet valves went bad on an all in one washer/ dryer, and some of the older propane furnaces can be a pain to keep running. Ive changed two furnaces over 14 years. IMHO extended service agreements aren’t worth the money. I have purchased them before and never felt like I got my moneys worth. I also realize that the dealer offers them to every purchaser to make money and they must make more than they lose or they would quit selling them. I would say that if you can afford to pay for some repairs its probably better to keep some saved in case rather than pay for repairs you may not need. If you can do the work yourself, you are much better off. Most dealers don’t want to help you after the purchase anyway so you will need to learn how to do some minor repairs and maybe a few major. Most repairs are pretty simple if you take your time. There’s plenty of videos on youtube to help And plenty of people here that would offer advice who have probably been through most anything you are going to come up against