The majority of full-timers have a mail forwarding address as their permament address that they use on the driver's license, registrations, voting, etc. When you want your mail you call or email them and they will send it to the nearest 'small' town post office c/o General Delivery. We never had a problem doing it that way.
What kind of address are you using now?
Full-Timed for 16 Years
.... Back in S&B Again
Traveled 8 yr in a 40' 2004 Newmar Dutch Star Motorhome
& 8 yr in a 33' Travel Supreme 5th Wheel