We relented and bought an extended warranty with our then new 2004 RV after the dealer's closer cut the price down to $1700, as I recall. I was not given a copy of the contract/warranty and had to request it from the warranty company. I read through it carefully and found that it was full of exclusions, loopholes and stringent requirements for keeping records and having periodic servicing done on the appliances, etc. These warranties go into effect when OEM warranties cease, so the warranty company is sitting on your money for up to 3 years. We never made a claim during the warranty period. With few exceptions, it makes more sense to set up a "pearl harbor" bank account to cover repairs, upgrades and other RV ownership expenses as they arise.
BTW, Our fridge, roof AC unit, and fresh water pump died at about 10 years, which may be about average.