If your goal is to avoid that, and you look 21 permanently a la Highlander, you probably want to get new one every thirty years or so, starting over as a “runaway teen” or “refugee” who lacks identity documents with a nominal age of fifteen.
Or just commit identity theft. That one you could probably do once a decade, or more; just keep a running file of unsolved disappearances of children and teens and pull another one out whenever the age more-or-less fits.
Some of us really liked Highlander