You bring up an very good point. It might be interesting to ask how much a policy would be for an RV that is 3 year older than what you have, when you decide to make the original purchase....that might give you an idea of just how much of a rate jump there will be.
3 years, means that there is a much greater chance of one of those appliances or RV parts failing, so they are hedging their bets, that it won't cost as much as the premium.....but it's sort of reversed from what your regular Auto insurance is (typically goes down as the car gets older).
Thanks for opening a few eyes.