I'm not denying that this has occurred, but I seriously doubt that the state can force you to get plates unless you have taken some step towards establishing residency in that state. For most people getting a job is usually the key to establishing residency. I suspect that many (most?) of those permanent rigs you described had occupants who were employed locally. We are SD residents and own property in TX. We spend half the year there but are not employed and haven't done any of the other things that would signal that we were becoming TX residents. We see no conflict in that; lots of people own property in multiple states, but you can only be a resident of one of them.