I stuck with Phineas and Ferb from the beginning (I remember the day of the premiere, even!) right until the end. But that show never really got bad. There were some episodes that weren't as good, sure, but I feel like the creators still had it up until the end. Last Day of Summer is pretty brilliant and I was very happy when Act Your Age happened, even though it was even more different from the usual formula than the show usually gets when it tries something new.