FWIW I got a launch iPhone X I gave to my dad with original battery now at 73% health, OLED screen burn in, and a broken charging port (wireless charging still works), and he’s still using it as a daily driver lol.

So while batteries certainly can go subpar faster, they can and do last much longer sometimes.

I also babied it and rarely charged above 80 or fell below 25, which may have played a part but who knows.