Find a Team
Unless you're insane you'll need to sleep and you'll be risking your health if you don't. If you're going to sleep you'll need someone else to play. Besides that if you gain popularity you're going to need people to read e-mails, post fan art, monitor chat, get food, etc. I think three people is the minimum you can get by with. These can't be any three people, they need to be people who are willing to exhaust themselves playing video games for an extended period of time and can be relied on to not get bored and leave halfway through.

Also, I think it's important that the whole team is involved throughout the event. It can be confusing and uninteresting if you have different groups of people participating at different times as if you were changing shifts. In other words, your sleep rotation should be set up so that only one (maybe two for bigger marathons) person is off camera at a time. For example, Brian, Dan, and John are running a marathon and Brian goes off to sleep for a few hours while Dan and John continue playing. When Brian comes back, Dan leaves to have a nap leaving Brian and John playing. When Dan comes back a few hours later, John goes leaving Brian and Dan playing. Their marathon would then seem contiguous to the viewers and you'd recognize the same guys from hour 1 as you would on hour 31.