As much as I truly enjoy the books (being visually impaired, I get the audiobooks), there will surely come a time when Jim Butcher writes himself into a corner since, with each one, he does seem to pack more and more in.
Didn't he say, though, that he'd stop after book 20 - although I doubt he will last that long. It'd have been logical to end it after Changes but I guess it's interesting to see him being the Winter Knight, maybe Cold Days should have been book 13 and then that'd be where it ended