There are quite a few services that offer mail forwarding service for RV'ers, and even bill paying. You could also have your income checks deposited directly to your bank account, then pay bills online.
If you know where you are going, you can ask your local post office to forward your mail to Your Name, General Delivery, Town State Zip
A good traveler has no fixed plans, and is not intent on arriving. ~ Lao Tzu