It’s not like there are people checking for immortals, I think it would be flagged by a dmv employee or something when they dont believe a clear 21 year old is actually 150. Let’s assume it’s current day im caught and not bring speculation on what the US is like in the year 2139 is like.
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.
As someone who isn’t an immortal Highlander, this works.
That sounds exactly like something an immortal Highlander would say
Continue having children throughout your immortality every 20 years or so. Make sure you have an child of the gender equal to your own, and on their 21st birthday, you switch identities with them. You sit for their picture on their newly issued ID on their 21st birthday, and suddenly its your picture that is the one of record for the legal 21 year old. Your child takes over you identity, grows old, and dies. Repeat ad infinitum.
what happens when the child is immortal too?
Child didn’t have to survive birth. I think that is what happens in highlander, he finds dead children’s names and takes them.