First off, only the manufacturer can issue a warranty. What you are looking at is an insurance policy with lots of fine print.
Personally I feel a service plan policy is a total waste of money on a trailer. There just isn't that many high ticket items that can fail.
Insurance is to cover things that you cannot afford to cover on your own, I would assume that if you can be on the road for years you must have some personal finances.
That policy may give you some peace of mind, but financially is a poor investment.