Earlier quoted context omitted.
Quoted post unavailable.
Do you personally know anyone who has been using the same iPhone for 8 years? I find that claim dubious.
Not quite as old but my Mum's still using an iPhone 5s from around 2014 which she had from new. She's not into apps so again, works fine for her as she doesn't need to be able to install anything. Thankfully homekit is still working on this and she's able to use it to tell siri to open the garage when she gets home.
Obviously these are very much edge cases, you can't find many apps in the app store still working on these older models.
I myself only upgraded from an iPhone 7 this September when the 14 came out. I'd had the battery replaced by Apple last year as it was a free recall thing which did massively improve its performance but it did eventually become too much of a pain in the arse to keep using.
I've got an old iPhone 5 which I keep for use as an occasional wifi hotspot too.