Read the actual policy, not the sales brochure, to see what is actually covered and what hoops you have to jump through to get coverage. After that understand that the warranty companies, actually insurance, are not regulated and they can "go out of business" leaving you with a worthless policy. In fact, for many warranty companies that is their business model. Then understand that they have access to a lot of repair orders so they carefully word their policies to eliminate common failures.
While you will hear many people say they have made money with their extended warranties, understand that the odds are not in your favor. They collect money from many to only pay out to a few. Also understand that the dealers who sell these "warranties" make a lot of money from their sales, often more than from the sale of the RV itself. Therefore, you will get considerable pressure to buy.
In almost every case, you will be better served not to buy the warranty. If you would be including the cost of the warranty into the loan of the RV, don't forget to include the financed cost of the warranty, not the initial purchase price, when making your decision.