When your id says you're 100 and you look 21 it's going to cause issues.

You want to get away from ever needing an ID. The wealth you gain from compounding interest should allow you to hire accounting experts who will handle your transactions and hide your wealth among shell companies. I think once or twice you could go with the "this is my child, me Jr" routine, but eventually you need to have some kind of emissary who conducts business on your behalf while you cycle through fraudulent ids and move around every 20-30 years.

The oldest person on record died at 122, and there's reason to think that there was fraud involved and she wasn't actually that old. By the time you were in your hundred-and-teens, you would have attention from scientists even if you looked your age. They wouldn't be forcing you to undergo medical testing if you didn't want to, but I think they would resort to force sometime in your hundred-and-twenties. If you didn't look your age, you'd have attention much sooner than that but people would think you stole someone's identity (that's what they think the 122-year-old person might have done) and not that you were immortal.

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.

It would be very easy. There are many places where money is all you need. Living in a shithole like the USA is the last place you want to be. Go anywhere you find Russian oligarchs or their kids. There are many micro nations that would gladly let anyone print any name they would like for a fee.

You won't be taken away for "study", you'll be taken away for pension fraud. Probably much earlier than 150.

Why would participating in studies be bad, though? Major pharmaceutical companies would pay you an absolute fortune in exchange for participation and you could advance medical science tremendously. You'd be a hero and get incredibly rich in the process.

The circumstances where you’d be most likely to run into issues is where age plays an active role—e.g., Social Security or insurance. But those are probably avoidable if you’re careful. Otherwise, there’s no law against being really old or looking young, if you’re not trying to claim age benefits—for anyone else where the date of birth wasn’t relevant to their job, they’d probably just ignore it or assume it was a typo.

Thats an interesting one if u happen to have happened upon a path to immortality lmk with that power i can help you rule the world. Forever.

I believe that most states require you to retake an ID photo every so often, same goes for passports. You could age relatively normally and still retain ID as long as you renew when it expires and update photos as required.

And it's not entirely out of the question that even with the same real birthdate, such a legitimate ID of an immortal could be overlooked.