I haven't done anything remotely like this since early high school, but I beat three of my favorite, but also shorter, RPGs in less than a week: Lunar SSSC, Suikoden I, and Suikoden II. I literally only had breaks for meals and bathroom, and probably played over 10 hours/day for 6-7 days straight.

I loved every second.

I had some binges through longer games as well (especially my first playthrough of FF7), but I don't remember the specifics.