One of the few things you can count on is that Apple will release a new iPhone every year, a new and improved model to the one you just bought. By the time that new one rolls around, they’re already classifying the old one as outdated and dysfunctional. So, contrary to popular belief, they do not put that iOS 10 update on your iPhone 5s to improve it. “Planned Obsolescence” is the term many people use to describe Apple’s decision to send problematic updates to all previous models in order to cause issues with batteries, apps not opening, connectivity and other problems. These updates will make your phone slower and, with enough updating on an older model, obsolete.
There is no reason that you should not be able to get four to five years out of your iPhone before you upgrade to another. They are well built, quality phones made to last. However, these updates can cut the lifespan by as much as two or three years. Therefore, anyone with a functional phone below the iPhone 7 should just ignore these prompts; ideally, you should still be on either iOS 8 or 9 for the iPhone 5 and 6 series. The software that comes with your phone already works perfect fine.
Also remember that once you update, you cannot reverse it. There are many ways that Apple will try to force you to update. One such tactic is that sometimes your phone will ask for the passcode but will write in small print that doing so will automatically update the phone sometime early in the morning. Down below, an even smaller button to opt out of this automatic update is the only way to prevent it. Another means, even harder to avoid, is that developers will update popular apps such as Facebook and Snapchat to be compatible with the newest iOS, which creates a disparity between your operating system and that of the app. In order to continue using it, you will most likely need to update your system. Hold out as long as you can and then either stop using the app, or update, but be informed about your choice.
The bottom line is that if you update an older model, you can essentially turn it into a paperweight. The battery and charging port can be serviced, as can other things, but repair stores can only do so much with an updated phone because many times, the phone will just short out new batteries or chargers. Be aware of what you are doing with your phone and also be mindful of the impact of buying a new, barely changed phone every year.