Okay, I've tried Android, and it sucks. Since I primarily use my Lumia 640LTE WP8.1 for Talking, Texting, Email & occasional websurfing, a lack of updates to popular apps I don't use does not concern me. However, without updates, what effect will there be on the basic communication functions of the phone? A basic qwerty feature phone would do.The battery is replaceable, and cases and such are at bargain prices...so long as the hardware doesn't break, how long will I be able to use the phone for these basic communications?
I primarily use my Lumia 640LTE WP8.1 for Talking, Texting, Email & occasional websurfing,
Regarding Calls and SMS your phone will continue to work as long as the hardware functions properly.
Email communications will also work fine for a long time as you can use IMAP accounts and it is very widely used among mail clients and Enterprise.
I also dislike Android, and refuse to discard my 620. I suppose, that as long as the internal memory doesn't get full, you'll be able to use the phone for many years. However, due to the lack of support, you'll start having issues when surfing the web. My 620 struggles to run websites filled with adds, as they consume a lot of resources. I also have issues when surfing on websites made with scripts that Explorer can't run due to the lack of updates. The main issue I'm currently having is the Storage Full message when trying to access whatsapp. That's because it cannot be moved to the SD, and the Videos and Music apps, which cannot be moved either, consume a lot of the internal memory. But if you're interested in using your phone only for talking and SMS texting, I guess it'll be useful for a long time.