Re: mail delivery
Snowbird,
It depends upon what state you choose to use as your domicile exactly what must be done. The reason that Florida, Texas and South Dakota are the most popular states for domicile is the fact that none of them have either a state income tax or any time that you are required to be physically present in that state to qualify as residing there. All three of them do accept a "private mail service" as a legal address for things like driver's license and insurance. They also all have reasonable costs for things like vehicle registration and insurance.
Which state is actually the best depends upon each person's situation. The two largest services are Escapees in Texas and Good Sam in Florida, but both of those states have numerous other mail services. South Dakota has several, two of which are particularly well known and have good reputations of long standing. If you plan to change to one of those states, it is important to realize that you must move your business affairs to the state chosen, just as though you were moving your physical presence there. In addition, if you are employed the state where you presently reside and work is not going to easily give you up as they probably have laws that require that you be a legal resident, as nearly all states do.
The domicile in some chosen state works very well for those of us who are fulltimers and who do not spend more than a few months in any one state. You do have to use care not to violate the laws of the state where your physical presence is, and a permanent job or home is one of those things. Another factor in the laws is that you must have some intention to return to that state when you stop travel. That is considered to be shown by the fact that one has moved his business interests to that location. Not everyone moves things like banking, but if the previous state is a sticky one about getting their taxes, you could be forced to do so.