I wouldn't call RV insurance a no-brainer, there are only a handful companies that will insure RV's for full time living. Allstate, and Geico, are 2 of them. Also there are some companies that only insure RV's. Look for companies that insure "Specialty Vehicles". Also Insurance companies are regulated by the state, so different States have different rules.
Also State laws have a lot to do with it, I believe in California your RV driving down the road is a Motor Vehicle, but when its sitting in a park it's a Mobile Home. You need to check with your state to see if they allow you to classify your Van as a RV.