Cruise America's Extended Warranty Service Agreements

I find that the El Monte refurbished rentals are approximately $10,000 more expensive for the same class, size, and year. It's good to know that most people who bought from CA and El Monte never had to use the extended warranty. Guess it would be good to have for the big ticket items like the engine, transmission, drive train, and generator. However, how many of these items fail completely and need to be replaced?