I write in spurts. Never on a schedule, just when I have some time and the 'mood' is right. Once I was on a tear writing non-stop for over 12 hours, slept for about three, and then went back in for another six or seven hours before passing out at the keyboard (TsukiRyoko, I'm there with ya!). I know this sounds silly, if not like an out and out lie, but that's how I write sometimes. I just go into a zone and time seems to disappear. All I see is the story and the computer screen as the story unravels before me. It's almost like a possession by the story, I'm there, but under the surface as something else controls the body.
And for those who are about to attack my 'moods,' I can focus my moods into the writing - when I have time to write. But sometimes, just sometimes, there is a block and I have to put the WIP aside until I can get a better feel for the story.