The end of the series. What keeps shows like this going is the romantic tension that makes the Fans keep watching. That's why some shows who put their main couple possibility together end up going downhill. So I'm going to say that it would be somewhere toward the series finale.
I don't mean to spoil it but... okay, i won't spoil it. I'll just say that Caskett Fans had better watch Always soon because all of my little caskett fangirl dreams came true.
