This is a very interesting dynamic because it is absolutely true that the phones are designed to last about 2 years. But the carriers also depend on this becaus

This is a very interesting dynamic because it is absolutely true that the phones are designed to last about 2 years. But the carriers also depend on this because in order for them to introduce new features and functions or to get new spectrum opened up for capacity, the count on the entire user base of phone essentially turning over every few years. If that pace slows down, it will be more difficult and take longer for them to turn up new spectrum.