Get some different rates. Check with your regular insurance carrier first.
State Farm does give a 50% discount on motorhome insurance IF you also have at least 1 car insured with them. By this I mean - you will pay annually what the cost would be for 6 months if you don't insure a car, so 50% less. You can also get a multi-car discount by having a car insured - that is another 15%. This would be as long as you do not need full-timers insurance coverage.
We are full-time and now have Progressive. They had the cheapest rate for the best coverages. Make sure your quotes have exactly the same coverage and deductibles to do a fair comparison.