I almost entered the 3-Day Novel Contest this year. I filled out the form and everything, but $50 seemed too much when I didn't even have an idea--much less an outline--so I never sent in my entry.
If I had, I'd have been writing for the better part of 13 hours by now. Instead, I spent the morning getting my weekend errands done (oil change, grocery shopping, bought a wedding gift for a cousin, post office, car wash, shameful fast food lunch with fries). I had a notebook with me as always, but I only wrote about a page of notes on my current project. If I was in the contest, I'd have aimed for a minimum of 10,000 words by noon.
Could I do it? With a solid outline and well-thought-out characters, sure. I've written 10,000 words in one sitting before, and my head didn't even explode. The trouble is keeping that kind of pace over three days; in fact, really it's two days, because you want to leave time to do some triage editing before you send the entry in.
But I'm glad I didn't enter after all. My goal for September is to strip down and rebuild a novella I wrote two years ago. The characters are great, the setting interesting, but the plot is junk. By the end of the month I want to have the new rough draft ready for revisions in October. And I have to get it finished by the end of October because I want to submit it to the Wizards of the Coast open call with plenty of time to spare.
Plus I want to do Nano again this year.