> If batteries normally last 3-5 years, I don't think we're going to start seeing most people keep their phones for 7-10 years.

I think they will eventually. People hang on to their computers for longer and longer because old ones are just good enough. Phones are getting to that same stage in their evolution where they stopped evolving by leaps and bounds between generations. A seven year old phone like an iPhone 11 for example is perfectly adequate for a lot of people.

There are two real blockers from keeping a phone for so long, official software support and battery life. If some big manufacturers solved the first with extended support cycles, which is an expensive one, why not solve the second too?