Having been working on a science fiction novel that covers economics, futures markets, genetic uplift, AI, finance, combat, and orbital mechanics, and having been working on it for 3-5 hours per day for 18 months (
http://morlockpublishing.com/the-book/ ), I'm somewhat underwhelmed with anything that can be done in three days.
I suspect that I spent more than three days on researching lunar geology, minerology, titanium refining, the compresibility of air, etc.
Not to mention that my first draft took 9 months, and my revisions have taken 12 months.
Some things require iteration and polishing. Writing, IMO, is one of those things.