For most people, these extended warranties are not worth it. For some people, they will be worth it. If it turned out to be "worth it" for most people, the insurance companies would soon be bankrupt.
My experience with RV appliances: I had a houseboat that was more like a floating RV. The (RV) fridge lasted for 25 years, the water heater for 30. I currently own a 5th wheel that was built in 1994 (Alpenlite). Its fridge lasted 15 years, and the water heater lasted 21 years. Its furnace quit after 22 years, but I was able to fix it by replacing the sail switch, ignitor and control board. That was 5 years ago. I currently own a truck camper that was built in 1987. Its fridge lasted 23 years and its water heater is still chugging along. Its water pump lasted 30 years.
I have owned three travel trailers, two 5th wheels, one truck camper and that houseboat over the past 31 years. I was a fulltimer for 8 years on the houseboat and 4 years in the Alpenlite 5th wheel, but the latter is stationary (on my property). Although I only lived on the Alpenlite for 4 years, I have owned it for 12 years and the fridge has been running 100% of that time (the new fridge, which was installed when I bought it in 2009). That fridge is still working fine.
The rest of them had all been used sporadically, maybe for a total of two months out of any given year. Several of the travel trailers and the other 5th wheel weren't owned long enough to know how long their appliances lasted, although nothing broke on them while I owned them. But when things do break, I fix them myself. I have never had a stove break. Even the a/c in the Alpenlite still works well, after 27 years.
As a general rule, I don't buy extended warranties on anything. I did have one on a motorcycle, but the original owner had purchased it and I could have it transferred to my name for $40, so I went ahead and did that. I never needed it though, so it was a wasted $40. For that little amount of money, I figured it was worth it just for the peace of mind.