It's really a matter of establishing residency in a given state. We have residency in SD via Americas Mailbox. Our motor home and toad are registered in SD and our drivers licenses are from SD. We have a winter home in AZ where we also have a small pickup which is registered in AZ and stays in AZ.
The issue is residency. If we stay in AZ for over 6 months we must become residents of AZ and then would be required to register all of our vehicles in AZ. Because we are only in AZ for less than 6 months we can maintain our SD residency. We document all of our time out of AZ very carefully to ensure that if the state of AZ comes after us we show that we are not in state long enough to establish residency.
As another poster stated, consult an attorney.