But if you look at ebooks on amazon it's getting lot more common to have serials. Shorter books, cheaper price, fast turnaround. My favorite is Wool, which has done 8 books in last 20 months and is excellent.
John Scalzi's "The Human Division" is another serial that Amazon has really been pushing me to buy that I can only assume is worth it. Second for Wool being excellent.
Not really. Since my wife started writing she's averaging about 2 1/2 to 3 months. And that includes the 2-3 weeks waiting on the copy editor.
I don't think it would be that hard.. also, once you have a back catalog, your newer books will raise interest in your older books until it becomes more self-sustaining... fewer sales of older books keeping a consistent income.
Unless you are Isaac Asimov, and your writing produces about 8 books a year on average during your whole lifespan.