You've all given me valuable and inspiring ideas, thanks.
I think I'll decide to use the bunch of contexts (or whatever you'll call them) that feel "right" to me (that means, probably too many of them). The idea of having one big NA list just makes me feel too anxious right now (I'm busy filling in my inbox, but don't really have solid days to work on it.)
When I start processing I might change my mind about my contexts (I'm expecting to).
Now I can start worrying about paper-vs.-plaintext files