I'm currently using >7 year old Android phone. The batteries on these things are child's play to replace (especially after you've done it the first time and removed the pointless adhesive in the battery compartment). I will consider upgrading once new devices return to feature parity with my current device (apparently never).

While I'm of course an edge case, the fact that Google, Apple and Samsung all provide >5 years OS support for devices now (and battery replacement services) suggests that many people hang onto their old phones for a long time.

That said, I'm not using 7 year old software on my phone. That would be insane. And my browser (fennec) was updated just a few days ago.

You get the guy at the mall to swap in a new battery for $50 in most parts of the world. Its cheaper to do that every few years than buy a new phone, and I have several family members who refuse to upgrade on principle, because modern phones grew too large for their hands/pockets