The normal "buy an extended warranty or not" argument has been beat to death and you'll find many threads on it.
Your question is a bit different since it's for an 8 year old coach. I suspect any warranty you'd find that would be willing to cover that coach, the premiums will be absolutely outrageous. Also, be REALLY careful of the aftermarket warranties and all the exclusions. Warranty companies are famous for excluding parts of components so they basically never have to pay.
On a coach of that age I'm basically with the majority thus far. Save the money and be your own warranty company.