I am still using my 13 Mini. I got it, because I knew that it would be the last Mini Apple does.
I plan to use it, until I need to charge the battery every 15 minutes.
Just so you know, the batteries are replaceable ;)
Same boat, though with battery replacements, I think what will actually do me in and force me to downgrade to a newer model will be when they stop supporting OS security upgrades. I'm perfectly happy to keep replacing the screen protector and battery until that point.
I have a 13 mini that is hanging on by a thread and you will pry it from my hand (because I can actually hold onto it). I'm actually considering finding a refub because I prefer my old-fashioned artillery to the 6.1".
The larger phones barely fit in pockets, fit poorly in running packs/biking gear and are just generally inconvienient for being active with them.