This has become more and more of a thorny issue due to Real ID laws that now require you to "prove" your physical address before you can get a driver's
license in most states. That rules out using a PO Box as your only address--you need a street address somewhere that is your "residence" address, and in many states a business address won't cut it--the computer will spit it out and say no go. If you currently have driver's licenses and an address someplace it might be worth it updating them so you have a few years before this becomes a problem again. My usual
advice is to find a trusted friend or relative that will let you use their address as your "residence" and then have as few things as possible actually sent there. You can then use a good mailing
service, like St. Brendan's Isle, to actually receive and forward the bulk of your mail. Some cruisers also use SBI as their "residence" address in
Florida, which does have tax advantages, but wouldn't really
work for you until you take off cruising. If you are staying in
Massachusetts you will probably want to use the trusted friend or relative suggestion, and then get a PO Box or a UPS Store box for the bulk of your mail. You generally only need the "residence" address for your driver's
license, car
registration, voting,
income taxes, and possibly your
insurance.
Here's a link to the Massachusetts ID requirements for licenses.