I generally upgrade every 4 years too these days, at least the last few times and for the next upgrade. Let's see if I can remember my whole phone list.
- Motorola M301
- Ericcson 628 or 688 I don't remember which (or whatever the modified name was on one2one back then)
- Nokia 8100/8146 (you know, the ACTUAL matrix phone)
- Gifted Nokia 3110 or 3210 (8100 broke down)
- Nokia 6100/6126
- Sony Ericson T68i
- Sony Z1010 (my first phone with a camera, spoiler alert, it was terrible)
- iPhone 3GS
- Samsung Galaxy S2
- Samsung Galaxy S4
- Samsung Galaxy S6 Edge+
- Samsung Galaxy S20+ (current)
Wonder if I missed any that were that forgettable?
Generally an upgrade outside of 4 years was because there was a feature I particularly wanted or needed. On early phones this was quite often (think SMS support, WAP, EFR, GPRS). But then contracts were generally for 1 year so it didn't matter too much. Later phones it's been 3G/4G/5G/Wifi calling etc that generally drove upgrades.