Food and supplies won't last forever. He needs a new look and a new identity. Not so easy to come by for the ordinary citizen, and even harder to maintain once you get it.
It used to be possible to go to a small county where deaths are not reported to the government, find someone about your age who recently died, and then apply for a lost social security number in their name. Unfortunately, most people who are hiding from the government eventually slip up, either through confession or a reversion to their old habits and interests.
Brian's gonna have to give up Instagram and Pinterest forever.