My prediction if you buy one on a vehicle....

A few years from now the a/c compressor will go out entirely on May 1. The shop estimate will be $1500 for genuine factory parts R&R. You'll "remember" that you bought an extended warranty. You'll have the dealer check it out for you. Dealer will say, "Hey ...you did buy the extended warranty and it would cover the a/c R&R. But...it expired on March 1!

I know for a fact this can happen.