Be very wary of buying an extended warranty. Do your homework before you sign on the dotted line. Check out the company with BBB or other organization to make sure you're doing business with a financially sound and reputable company. You could find out the hard way that not only was your claim denied, the company was no longer solvent or had disappeared.
If your RV is several years old, you might be better served to stash away the cost of a contract.
OF course these are just my thoughts, based on personal experience.
Steve K