My MIL leaves her phone plugged in 24/7. It died today and I wondered if leaving it plugged in all the time could damage it. (Is only a couple of years old.)
Yes, but…
Not in a way that causes the phone to “just die”.
Instead, it eventually starts causing the battery to swell. And it will swell enough to either pry the case apart (I’ve had that happen on two phones and a laptop computer), or crack the case, before the phone stops working.
And when that happens the phone is becoming a fire hazard. It’s recommended that you replace it ASAP, and in the meantime drain the battery and don’t plug it in again other than for the short time needed to transfer stuff to the replacement.
Now what’s silly is that I’ve had a couple of Android devices that detect you’re leaving them plugged in a lot, and decide to limit how much charge is in the battery… to 50%.
Why not 90% or 95%? That would make the thing a lot more prepared for the occasions when it can’t be plugged in for an extended period. {And it’s what my current laptop does. It’s been plugged in for over a week. The battery indicator says “Charge: 95% (fully-charged)”.}