I have found that once in a while, I see one sale of a book, and then a day later every story in my backlist goes at once, so I figure those are new readers who liked something they saw and went for the rest. But it's not as predictable as people buying the new things I put out. Nevertheless, a big backlist is a nice thing to have.

I think discoverability is the next big hurdle. Konrath isn't a good example of how to solve that problem; traditional publishing gives a big boost to visibility that translates readily to self-publishing, so they never had to contend with the "no one knows who I am or that I even exist to buy my books" challenge.