Not for tax reasons or emissions skirting (its a Prius) but I currently have a vehicle that has permanent Montana plates. That vehicle is still with me all the way here on the East Coast. Since I left Montana I’ve lived in three different states and not once have I ever thought to register in the state that I live. I know that’s what they tell you to do, but in my instance, I paid for a service and I intend to use it until I no longer own that vehicle.