I upgrade roughly every four years. I'm on a 12 Pro Max right now, so that means 2024.I'm having no performance or other issues with my 64GB iPhone 11. I'm running the latest iOS 16 beta and am happy with it. Let's see if the 15 next year makes me think about upgrading.
The iPhone 12 series has the Apple A14 SoC, which is actually faster than my 2017 27" iMac Core i5-7600. In that context it seems ridiculous that people are complaining that the iPhone 14 non-Pro series have "only" A15.
BTW, the reported average in North America for phone upgrades is 3-4 years, which means some don't upgrade for 5-6 years.