So this is going to change how people use twitch. Basically the tl;dr of it is they are removing past broadcasts entirely. The past broadcasts can be made into highlights that WILL be saved forever or exported.
ALL archives of past broadcasts WILL be deleted in the coming weeks! So export your most cherished videos now! You can read the whole blog here: http://blog.twitch.tv/2014/08/update-changes-to-vods-on-twitch/