Someone I know was still using an iPhone 5C that still worked great until suddenly when they made an outbound call they got a recording that the phone was no longer supported. Apparently AT&T is yanking out all the 3G antennae. Upgrade or lose service, he was told.
Sure, at some point, the technology you're using goes away. Old analog brick phones from the 90s don't have anything to talk to anymore. But usually "end of life as determined by the cell company pulling down the radios" is far longer than most phones last/are useful anyway.
The other limit is that apps stop working on out-of-support operating systems. The App store on that iPhone 5C wouldn't let anything install, just like on my hand-me-down iPad 4th gen. If support ends in year 3 of your ownership, expect all your apps to quit.
Indeed, and I'll point to "security updates" as another thing that I, at least, consider non-optional with phones. I have enough core access to things (my Google account, various things that use 2FA, some building access stuff) that I just won't run past regular OS support at this point for my personal device. I don't mind keeping phones around longer for low-priority stuff (my old 6S is now the Family iPod - a bunch of music and books for listening to in the car and around the property), but I don't consider my Spotify account to be particularly high privilege.
I'm paying attention here. I've avoided buying i-products, but a phone that lasts 6+ years for $300 or less is something to consider.
Indeed. It was
really funny watching the Android review sites as they got this $400 (new, MSRP) device that literally outperformed $1000 Android flagships, with Apple-duration OS support (vs Android, 2 years, maaaaybe... and maybe some security updates if you're lucky), etc. The reviews more or less were uniformly, "Well, shit. Uh, this is a great phone for half the cost of a slower Android device, how attached are you to Android?"
How much does a battery replacement cost?
Around $30 if you do it yourself, probably $100 retail for someone else to do it. Not sure exactly on the 2020 SE, but that's around where similar devices are and there's no reason to expect a huge change from that in 4-5 years when you need to do it. Plus, newer iOS devices support "optimized charging" that will only charge to 80% until you're about ready to grab the phone if you have a consistent pattern. If you plug in at night and always pick the phone up around 7AM, it will charge to 80%, then top off from 80% to 100% in time for 7AM, but not before. It helps avoid the fully charged state, which is hard on batteries.
Are there any issues with iPhones and changing carriers?
The new ones are generally sold unlocked with support for all the major bands, so they will generally work with everything. My wife's SE is on Project Fi at the moment, and even though I don't think she gets full carrier diversity, it works fine. I'm on AT&T Prepaid.