These phones cost more than some MacBooks - I’d expect a similar level of support for them which is 7 years min. Only reason we classify 2 year as “good” is because that’s what we have been conditioned to expectWhy 5-7? For dev purposes? 3-4 years is good for OS updates. Security updates should be longer.
Personally I don't keep any of my devices beyond 3-4 years, iPhones or Android. Most just 1-3.