I have an opportunity to visit NARA in Washington DC in July. I'm contemplating whether to spend a couple of days at NARA to research what I could not find anywhere else, e.g. online, microfilm. So, have any of you visited NARA is Washington and what/why should I go there? I'm concerned that if I can't get it on microfilm (interlibrary loan) of find it online, I would never find it at NARA in the bazillion records they have. How should I plan a trip there and how would I maximize my time?

Ken