Day 01 - A book series you wish had gone on longer OR a book series you wish would just freaking end already (or both!)
Gone on longer - I guess I would have liked another Harry Potter book or two, about what they did when they left school. But that's so NOT an original idea!
Series I wish would end - The Wheel of Time by Robert Jordan. Not that I haven't loved it, but it has taken FAR TOO LONG and some of the books could have been condensed a little. I have often wondered if he realised that he was onto a money spinner and decided to extend the series. As for a definition of too long - he went and died before writing the last book; a new writer is hired to write the last book from his extensive notes - that 'last book' is now going to be three last books - I started reading this series before my 17 year old daughter was born, for goodness sake, and she will have a driving licence before it is finished!!!