When talking about this issue, we need to distinguish between two situations.
One scenario is that, assuming our iPhone 8 Plus’s battery and system are in good condition, it can last a long time—even more than 5 years.
In addition, if the iPhone 8 Plus cannot fully meet user needs due to aging hardware and software updates during use, then this problem depends on the user's attitude. For some users who pay great attention to configuration performance, they will replace the iPhone 8 Plus in a relatively short period of time. After all, nothing is more important than their own needs. For some users who are very loyal to old mobile phones, they will look for some alternative measures, such as changing batteries, deactivating infrequently used applications, etc. In this way, the service life of iPhone 8 Plus can be further extended.
In short, for the iPhone 8 Plus, its future has a lot to do with its users. If the user cherishes it, does not pay attention to configuration performance, and is willing to take maintenance measures, then the iPhone 8 Plus can continue to be used for a long time. But if users focus on performance configurations, or if Apple launches more attractive products, then replacing their phones may become their only choice.