One day I spent a whole day playing Pokemon Crystal.
I used to play it for long sessions a lot after my copy stopped saving files, and I did it a lot when I went to my granfather and grandmother house in school break. I was always discovering new stuff in the early game parts I,used to plsy and loved it, but I also liked to go as far as I could, and one day I simply played the whole day.
I woke up 6 AM and grabbed my GBA, plugged the charger on so I wouldn't have a problem playing and having full battery when needed to unplug it, so I played until launch time and this time didn't stopped to eat, I ate while playing, I only stopped to take a bath but it was always on and I grabbed it again right after it, and only stopped playing 11PM when I went to sleep.
So 17 hours more or less.