Scott brings up a good point. Just because you have an ESP does not mean that you don't need to take care of your rv. Ther have been posts on the forums where people have had repair work to the time of $10,000 but the ESP covered it minus their deductible.
They are always a gamble. Never bought an extended warranty on anything until I bought a car in 2007. Never used the warranty thankfully. Bought one on our TT. We bought three years ago, because I wasn't sure if we would be able to pay $1000 to repair something. If we couldn't, we would leave to let it sit until we could. Never used it in 3 years and after trading it in on the mh, we got a partial refund (about half of it as it was a six yr plan). Have it on our mh now. Hopefully it will be a big waste of money. I did get get 6 yrs of platinum + ERS though. ;)
If you can self insure,it's always best. But many of us can't. That's why most states require car insurance through an insurance company. Although California had a way for you to prove self insurance. Not sure if they still do or if other states do as well. Just like regular insurance, it's someone that we pay that we hope we don't ever need.