I'm a person who tries to only replace their stuff when it breaks, because buying and configuring new all the time is just too much mental overhead. But when I do, I research my options for quite a while.
I had to stop using my Galaxy S2 because Google Maps became too slow to be usable on it (note that I'm not saying the phone became too slow. The phone didn't change.).
Now I've been using a Galaxy S5 for probably 7 years. I had to fix some things - like the power button - but you can find third party repair instructions and parts online easily. All I needed was a few minutes, some glue, and a screwdriver.
Obviously both phones run Cyanogenmod/Lineageos.
To be fair I already tried upgrading again, but so far I haven't found a likely candidate. There's some brands that market themselves as repairable, but I don't trust them to be around in six years and don't believe they have a community that would support the device independently with third-party spare parts.
For e-readers I'm using Kobo devices for now. Their plastic shells aren't particularly repair friendly, but their internals are (they use actual micro SD cards in a slot on their board for "internal" storage, with some Linux OS on it.).
My Thinkpad is 8 years old, so are my Dell screens. Both are still adequate by modern standards. In fact my old hardware keeps me honest in my everyday work as a software developer, by not allowing me to write software that is ridiculously slow and power hungry. Most of the world cannot necessarily afford hardware that is much faster than that (did you know Twitch is close to unusable on the vast majority of hardware in use today, while YouTube is perfectly fine? Stuff like this matters if you care about more than just the western market.)
The only electronics I keep "up to date" is a gaming computer. Depending on the titles you want to play, there's really no way around this. But at least desktop computers are somewhat modular.