Just don't burn yourself out, Lisa. I went for a 24 hour session reaching 17K. The time within that 24 hours with actual writing was closer to 17 hours though. I took lots of breaks. Closer to the end of it, I was so tired and my hands were cramped and I kept complaining about not finishing and then I did finish with an extra 100 words lol. The next three days, I hardly wrote. I think I only got an extra 500 words, though I was revising/expanding.
I suggest you pace yourself.