While I agree that this is nice, many people upgrade their phones every 2-3 years anyway, just because of the hardware/battery. For them, this is not a selling point.
Anyhow - the main reason I even commented was that people in the antique iPhone camp /regularly/ say they'll never go to Android cause the phones don't last. I really think people would like to keep their phones for as long as their laptops. And iPhones are the way to do that and that it is a selling point.
The first iPhone I bought was a 4 in 2010. I “upgraded” to a 4s because I got a much better deal through my employer to use Verizon and the 4 had separate GSM/CDMA versions. My son used the 4 from the time I switched from Verizon to T-Mobile until 2013 and upgraded up until iOS 7.
My next upgrade was to the 5 and again it was because of a change of carriers and Verizon wouldn’t unlock the GSM part of the phone for domestic use. The 5/5C were the last 32 bit iPhones.
I consider the first 64-bit iPhone to be like the first Core 2 Duos. At that point the phone was “good enough” and fast enough for most people.
My first 64 bit phone was the 6s in 2015. My son is still using it now with an Apple battery case. I would have kept it, but I needed a larger screen (iPhone 8 plus) to watch text heavy technical videos and the battery life is much better. I don’t see any reason unless I physically damage this phone that I won’t keep it for another 4 years.
I’ll probably replace my 9.7” iPad before I replace my phone and I don’t see myself doing that anytime soon.