I use State Farm for my various vehicles except my boat. Currently my Audi has full coverage. My M3 has a lower premium because it's in the "driven under 7500 miles a year" status. My motorcycle and Jeep are both suspended (they only have comprehensive) because I'm not using them.
State Farm couldn't touch the rates I was getting on my boat.
My former next door neighbor is an agent for
www.boatinsurance.net and he finds me the best prices. On my current boat we got the best rates through Progressive. With my progressive, I had him drop/lower key coverages during the winter when I wasn't using the boat. this lowered my overall premiums and I just put them all back up to the normal level by sending him an email. So I was able to make it happen with Progressive and an agent willing to make the changes for me in winter/spring.