I once played for almost 4 hours in a single session of Black Ops 2 zombies
I think, the longest run on zombies that I have ever played was about your amount of time on the map Moon. When the map came out, all my friends were excited and tried to figure out the secrets to the level. I know we stayed most of the night. The send longest run I think was on the map Buried. My team and I ended up quitting because it got boring after a while. I kinda wish it was like those days now.