My husband is now thinking of transitioning from his work-issued iPhone 7 to my old iPhone 8+. He's wanting to know how long the iPhone 8 line will be viable. My guess is 1-2 years. Thoughts?
That would my expectation as well. The iPhone 6s is still supported, so it would be surprising they would cut support for iPhone 7, 8 and X in the next year.
My guess is at least 2 more years for the 8 and 8 Plus. Most likely until iOS 17. Even then, it will still be a good iPhone with iOS 16, as long as the battery is good.