One of the many reasons we don't want to buy another new RV. GMAC jacked our rates up really high at renewal time when we bought the 2009. So far Progressive (thru AON) has gone down nearly every year on the RV, but up on the F450 so outgo has been level.
We've also had Nat'l Interstate (also through AON). I'm waiting to see how high it is this fall, cause we may get new quotes come September to see if we can save a few $$$'s.
There are other brokers besides AON who can give you multiple quotes. That makes it easier to decide whether to switch or stay.