I'm planning to upgrade from a 12 mini, which partly influenced my choice of years too (having seen 3 year data was the main part!). If I had a 12 Pro I think I'd have kept it for an extra year, but the battery is just not sufficient for how my phone use has changed.

I think furthering your extra details here too is I saw someone point out that one of Apple's slides for the base 15 was comparing its performance to the base 12. Apple knows how often people upgrade. Picking the 12 as a comparison point wouldn't be an accident — we're the single largest target audience for the 15. And in a year, they will in all likelihood compare the 16 to the 13 for the same reason.