Curiosity: Some facial biometrics are explicitly designed to they can't change over time, barring an accident or similar. They look at features of facial geometry such as eye versus nose positioning and similar kinds of things set by bone structure.

They're surprisingly hard to intentionally defeat. Growing a beard, putting on weight, etc. won't do it.

I looked into this some time ago, when I didn't want to be tracked. It turned out to be annoyingly hard. And e.g. "wear a hat and mask" makes you rather conspicuous.

The increasingly universal cameras are rather effective at knowing what you're doing at all times.