I don't have any experience with 3rd party extended warranties but many of our members here do and I hope some of they weigh on on their experiences.
Over the years, from what I have read, many of these extended warranties are so exclusionary that buyers are a bit dismayed when they try to claim against them. Then on the other hand, I've read stories over the years of a couple of plans that cover a lot of items on an RV. Wishing you the best in your search and whatever you arrive at, be certain that you are crystal clear on the exclusions and that you're okay with it not covering those items/areas.
Many RV owners advocate saving an amount equal to what you are quoted for extended service contract monthly in a SEPERATE bank account, and drawing from that if you need to. Having worked in an equipment support field that offered service contracts, it was my observation that a least there no effort was made at model-by-model repair costs, but rater a flat percentage of the purchase price was the contract price.
So many of the RV extended warranty agreements exclude frame and suspension - vital elements of your rolling house.