How Frequent is Too Frequent?

With the advent of e-publishing, readers no longer have to wait months on end for the next new release from an author. This is also a major plus for authors, who no longer have to wait a year or more for their next book to go public. While, in the meantime, they keep writing and are accumulating a stockpile of finished works like a squirrel gathers nuts in the fall. Unless they have more than one publisher, and can have several new books premiere within several months.

E-publishing has helped authors tremendously. But at what point does frequent become too frequent?

I've seen authors comment that a self-publisher (of which I'm one) should space their new books out. How far apart, I ask. A month? Every other month? Every third month?

Say an author has been proliferate, and has managed to write three books within a span of a summer. Should she sit on those books (while she continues writing) because she already have 2-3 other novels releasing between now and the end of the year? Or should she go ahead and put them up for sale after they've been edited and formatted?

Authors and readers, I'd like your opinions.