Personally I think this all depends on your content and how interesting you are. If you are trying to do a 2 hour show, but only really have 30 minutes of content that you are trying to stretch to fill the 2 hours, then you really shouldn't be doing a 2 hour show. I have a short attention span so I tune out pretty easily. If you have more than 5 minutes of stretching/filler, I'm not going to continue listening.