Maggie's comments about the 'creative well' were interesting. I think the reason I can write so prolifically is because my 'well' never runs dry in the middle of a project. Once I sit down to write, I write the entire book, start to finish, in one draft. It usually takes about six weeks. And there's always a residual 'wash-over' when I'm done that allows me to pick up another book and do re-reads on it in the next week or two after that initial draft.
I do have lulls, of course. What I do during the lull is work on marketing ideas, query letters, synopsis -- the 'mechanical' stuff of publishing. Then I'll go through my notes for books and something will set me off, and I'm off and writing again.
I'm not sure what's filling that creative well, but I hope it doesn't stop. I have seven or eight ideas for books that I'd like to pursue, and that's not counting my SciFi series about an alternate America. Heavens, there's a gazillion plot ideas there.
Guess I'll be busy for a while ...