The iPhone 8 was released on the 22 September 2017^[1], which marks the beginning of its update period. On the 18 September 2023, the iOS 17 was released, a next version of the operating system, which not made available for the iPhone 8, thus leaving iPhone 8 on the the previous version of the operating system, the iOS 16^[2]. This date marks the end of what we consider its update lifetime.

These two dates are 5 full years and 0 full months apart, which gives it AA- tier.