I have the Good Sam's Extended Warranty. It costs me $1740 per year and is a $250 deductible policy. In the 2 1/2 years that we have had the policy and have owned the now 8 year old coach, we are about breaking even. We have been paid for basement air conditioner repair, convection/microwave oven repair, satellite dish replacement, rear air bag on the suspension and a new lift pump on the engine. They pay for everything except some wearable items (brake shoes, wiper blades), misc parts, shop supplies, etc and the deductible.
I figure that when I have a major engine, transmission, refrigerator or other costly problem, maybe I will be ahead. Otherwise just gambling which is what any insurance policy is.
Back to the OP, I wouldn't buy the policy until the new-coach warranty has lapsed, unless you can really lock in a low rate.