Although I've got to say, the headphone jack might be the last straw for me ... my iPhone SE could be my last iPhone if a reasonable alternative materialises ...
Same. I’m holding on to my 6s until its last breath. I replaced the battery recently and that boosted its performance back to launch-day levels, so I’ll probably keep chugging along for another two years at least.
I like small and light phones so I bought an Xperia X Compact at the end of 2016. It's more or less the same form factor of the SE and it still works very well. Unfortunately its ticker (9.5 mm vs 7.6 mm) and it weights more (135 g vs 113 g). The Xperia Compact XZ1 from 2017 is 2 mm less tick but weights even more (140 g). If I could make me like iOS I would have got a SE immediately. The Compact is probably the best small phone in the Android world but I stopped researching phones. I'll start again when the Compact will be about to die. I hope it lasts at least as long as my old Galaxy S2, 5 years.