It depends if we’re just approaching this from a “physically functioning” standpoint, or from a “software/support” standpoint as well.

Personally, as soon as a phone no longer supports security updates, I get a new one. Pixels offer 5 years of security patches now, and I believe the latest Samsungs are doing the same. iPhones are well known to offer 5+ years too.

So personally I’d go with one of the latest Google, Samsung or Apple phones.

I know a lot of people don’t seem to care about how long their phone gets security updates for, so if you don’t either then just ignore everything I said :)