Worked on the bulk of it over the course of a day, on and off. Thought about it for a while before that though (when I was unsure if I was going to apply). This was my third time applying[1], so I basically have the questions memorized at this point.
Oh, and I've been recording every thought and idea for the past three months (some of my lists: http://grab.by/rKOY), so filling out the application was mostly compiling those thoughts into readable form.
[1] Different ideas each time, spanning 3 or 4 years. Funny enough, last year I got an interview. By that measure, this is a regression :)