When Is A Series Too Much?

So we all know that authors love to write book series and that we love to read them. But my question to you today is have you ever gotten tired of a series? Have you ever thought that it was becoming too much and needed to end? I think it's cool to read 4 or 5 books about a certain person but once you get to book 15 and book 20 I lose interest. It's only so much you can do with those characters before things get cheesy and stupid.
So what book series have you read that you felt lasted too long? Do you even like to read series books at all? Join the discussion below!