You cannot help but be impressed by this. I had my last phone in storage for a week and it died. But six plus years (am I wrong or is six plus years seven years? Just seems like basic deductive logic) and Nintendo DS (3DS, 3DS lite, 3DSx, 3DxYz or whichever model this is) turns on and still runs at 80% power. That is exactly why Nintendo has such die hard fans.
Because in a lot of ways, they earn them by just being a damn good company who makes reliable products.