Originally Posted by DoctorOhh
If a series is fully available and I am enjoying the read I will go back to back until either I complete the series or alternatively until the series turns sour. Once a series turns sour I most likely will move on and not come back.
That's a very good point. Many authors take a new direction that formerly faithful readers may not appreciate or run out of (creative) steam. I rarely come back to a series once its gone sour.
I can't recall if I ever read a lengthy series back-to-back. (I don't think Girl Genius counts.) If there are only a few books I might be fascinated enough to get through those (if they are available to me.) Since I often read several books at once, my usual reading patterns predispose toward taking breaks between installments (sometimes with another series).