What item have you been using on a daily basis for the longest amount of time?
Sometimes I will use something and realize I've owned it forever. It's a nice change in our throwaway reality. I think my personal record is a bicycle multi-tool I got for one of my first bikes, ~25 years ago. Still have it, still use it. When it comes to electronic devices I have a Panasonic mini Hi-Fi from ~2005. Never felt like changing it.
You got a rare immortal battery!
Every so often I encounter a device with a battery, rechargeable or not, that's lasted an insane amount of time given its size and use