The first computer I ever bought with my own money was an SE, bought second hand on a very tight budget some time around 1992. My mum used it to write letters after I upgraded, and my younger sister used it for school work after I left home in 1997. I guess it was finally retired some time around 2000 and it was left in my mum's attic ever since.
I started worrying about that the battery might be eating it from the inside out when I got into this hobby around 2018 or so, but never got around to retrieving it until two years ago.
First thing I did was open it up and check, the original soldered Varta battery was still intact and everything looked ok, so I plugged it in and turned it on.
It booted right up and still knew the date, and was only two hours off from the correct time.
That battery finally gave up about a month ago, at 38 years old.