Anecdotally, the iPhone in my post did have its battery wear down to the point that it had the "slowdown" thing enabled (can't recall what it was actually calle

Anecdotally, the iPhone in my post did have its battery wear down to the point that it had the "slowdown" thing enabled (can't recall what it was actually called). It was somewhat slower, but I wouldn't call it unusable. Maybe it depends on what people actually do with the phone. Google Maps, web browsing and such didn't seem to be that different. I then went ahead and disabled that thing and, sure enough, it started randomly crashing when the battery wasn't full. I then went in and changed the battery for the same price as my previous Samsung's battery would have cost (plus the annoying fact of having to schedule the visit). It did get somewhat faster (not sure whether placebo or not) for another 2-3 years until the battery started swelling and I replaced the phone (I need it to be relatively waterproof, since I use it often as a GPS on my motorbike). I do concede that I did find it weird and user hostile that, once you'd disable the "protection" mode, you wouldn't be able to turn it back on. Just like I find it odd that that specific model couldn't do the "trickle charge overnight" thing. And that my current iphone14 pro can't be told to stop charging at 80%, whereas newer models can.