Just because a new iPhone comes out every year doesn't mean it's a worthwhile upgrade. It all depends on how old your "old phone" is.
At the rate of recent incremental improvements, I think it takes and will take at least 5 years before a new model seems worthwhile. And in the future, as there's less & less to improve on, the time span will stretch even longer. The days of 7 year upgrades are upon us (if the device lasts that long). My iPhone is 5 years old & still works the same as when I got it. (Original OS)
At the rate of recent incremental improvements, I think it takes and will take at least 5 years before a new model seems worthwhile. And in the future, as there's less & less to improve on, the time span will stretch even longer. The days of 7 year upgrades are upon us (if the device lasts that long). My iPhone is 5 years old & still works the same as when I got it. (Original OS)