O'Dark 30

I listened to Friday's O'Dark 30 Podcast. I'd be curious to know how they go about deciding on a topic for a specific week. Is it based on the week's happenings (obviously this one was, cause it was Halloween themed) or do they find a piece they're interested in and build a show around that? Do they write out narration to transition between pieces, or is it off the cuff? And as a whole, why does KUT decide to have a 3 hour block of this show, rather than giving more shows an opportunity for a chance on air?