So this is really a thing?
Pretty Little Liars, The Vampire Diaries, True Blood, Lost, The Walking Dead, Merlin and so many other shows peaked in their 3rd season
I think Once Upon A Time will be canceled after its third season. It's just not the same anymore and the ratings keep going down.
Desperate Housewives season 3 was 100000x stronger than season 2 but it did go downhill from season 5 I thought, so it usually is either one of the strongest seasons or the weakest.