Which book series went on WAY past its expiration date?

The best science fiction and fantasy books are so addictive, you finish one book and immediately want to reach for the next. Until... they start to go downhill. Because the Law of Diminishing Returns applies to every universe. What's the book series that most outstayed its welcome? » 8/22/13 2:10pm 8/22/13 2:10pm

7 Reasons Why Scifi Book Series Outstay Their Welcomes

Click to viewWhy do so many amazing novels sprawl into so-so trilogies? Let alone blah tetralogies, or dull ten-book series? Blame "Herbert's Syndrome," in which a great writer gets tempted to keep writing about a popular universe, like Frank Herbert's Dune, long after its expiration date. (The Fantasy Review coined the… » 5/14/08 4:30pm 5/14/08 4:30pm