I keep my iPhone until it is no longer usable (Fingerprint sensor on my iPhone 6 eventually stopped working, my iPhone X had the battery swell up and bend the case) when this happens and I need a new phone, My wife gets whatever the latest one is and I take her old one (yes, my current iPhone 11 pro is rose gold... I don't care, slap a case on it.)

I give 0 shits about my phone, I actually loathe that I need one at all.