Well, so as not to upset any more super cute Lynxes, let me post my final word count.
It took until 10.10pm (though that included going food shopping (milk and chocolate to be exact), dropping books at the library, catching up with a friend for supper and having a 4 hour nap... which some might argue is not so much as nap as a serious state of unconsciousness, but whatever), but I have 10,018 words! Totally new words, new ideas to the story, all actually in sequence.
So, first appraisal of project: 10,000 words is a lot of words. Not just typing wise, but it is a lot of different thoughts and scenes. It involves a couple of chapters. Have found that the flow works for sections, but once you finish a scene or chapter, the flow appears to break up a bit, leaving you floundering for a few minutes as you try to work out what happens next. So today was not just four hours of writing, and didn't feel like this wonderful mystical experience, but looking back over what I've done, I'm pretty damn happy with it.
Bonuses to writing so much: I can see that it's going to help a lot with the coherence of the story, less likely that I will forget what happened previously, etc (though I do need to go back to my first book and check some details).
Am hoping that I'll sort of train up like a marathon runner so it becomes easier and easier to write in big chunks. Right now I don't feel mentally exhausted or anything like that, it's more that I feel dry, like my mind is searching for a cool, fresh glass of water. So will need to work on ways to quench that.
Back to my day job tomorrow for the first time in a week. Also try to knock out another 7,500.
Will let you know how work and writing turns out.