I definitely think you're right to compare it to research; that's an excellent way to think of it. Of course, that doesn't really with the question at all, because it makes the answer: always more than you think you need! Except when it's less than you think you need. Heh.

No one seems to have a good answer, though. I suspect it may be one of those timeless questions, like what style is best or how much description is good or where should I start and end the story or how many licks does it take to get to the center of a Tootsie Pop.

I suspect I just need to stop worrying and write it. Or at least get beta readers to reassure that I haven't become lost entirely inside of my own head.