Nintendo DS battery life and clock precistion

My parents are moving and I had to get all my stuff from the attic.This included all my old games and consoles.

When I opened my old Nintendo DS case, I directly checked if it would still turn on.

To my surprise, after it being in the attic since 2013 (12+ years) it not only still has green battery life, but also the internal clock is only 6 minutes off.

I am very surprised. Does anyone else have this experience? And how can it be that the battery does not leak over time? Also how can it be the internal clock deviates only 6 minutes in 12 years. This is below 1 ppm which is normally only reachable by temperature compensated quartz!

I am very amazed! Is this the Nokia 3310 of handheld gaming devices?