Because the Android ecosystem doesn't have a strong upgrade ability, app developers generally target a wide variety of OS versions, so when you do get cut off from app updates, it's really ancient versions, like gingerbread.
Seeing that my iPhone 6s bought in 2015 for $750 is still faster than most modern Android phones, I don’t think OS upgrades are going to be a problem.
App developers being forced to support older OS’s is not a good thing for the platform. iOS Developers can target the latest OS and all of its features and still support 5 year old phones.
My mom is running the latest version of Chrome on a Mac Mini from 2006 that I put Windows 7 on. How much luck would you have had running the latest web browser on a computer from 1994 in 2006? In 1994, I had a PowerMac 6100/60 (PPC 601-60Mhz) with 24Mb of RAM and a 250Mb hard drive with a 486 DX/2 daughtercard with 32Mb of RAM.
Today, I can use a 5 year iPhone 5s. Back in 2013, I would have been masochistic to run an iPhone 3G.
On the other hand, the day the new OS version or security patch is released for iOS, anyone in the world can go to the settings app and update their phone.
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.