My elderly mother has an iphone 8, which, it was recently announced, will not be compatible with the next OS update.
That part’s fine: she doesn’t need any new whiz-bang features. However, she does need security patches. When does Apple typically stop supplying those sorts of updates?
Security updates are part of every rendition of their OS so, when she can no longer get OS updates, she will no longer get security updates, either. If she is a careful user, she’ll probably be okay with the security she has.
IOS 16 is currently supported and it looks like Apple hasn’t announced EOL for it. Some releases, like iOS 12 continue security support after active support ended, so it’s hard to say how long iOS 16 will continue to receive updates. iOSs appear to be supported from 1-4 years. Apple appears to be supporting 2 OSs at a time now, so when iOS 18 comes out, expect support for iOS 16 to end.
This is why I am moving my daughter off an iPhone 8 tomorrow. She had my old X, but dropped it and had to use an old 8.
I dithered between a used 12 and a new 14, but the price difference was not huge and I figure it gives her at least an extra generation of OS updates.
This post may give some guidance:
Obtaining service for your Apple product after an expired warranty - Apple Support
Based on that article there is a hard cutoff at 7 years since sales were discontinued.
And a soft limit at 5 years where service might become a bit harder.
If you are talking about software updates it does not quite follow this setup
But it is around 5-6 years based on precedence the iPhone 6s probably had its last major software update with iOS 14(2020). which was 5 years after it was released(2015).
Once iOS 15(2021) releases iPhone 6s had had the newest version available for about 6 years.
The iPhone 6 on the other hand was released in 2014 and had its last major update in 2018 a total of 5 years with the newest OS. - SOURCE
This raises a fundamental question in my mind. Does Apple push security paths outside of mainline iOS updates, which we know end after 5-6 years for any particular hardware iteration? If so, for what support timeline?
Outside of some egregious security hole that Apple needs to fix ASAP on everything (which is very rare) I do not think they do. But, I am not an iPhone user so cannot say for certain.
(I have a very, very vague notion they had to cope with a major exploit in short order but I may be conflating Apple with some other system that got exploited and needed patching fast)