Just from my point of view, for a real, dedicated, worldwide, consistently growing audience, you need some sort of visual option on your podcasts. This would be easy
enough to do using Windows Live Movie Maker. Or on Mac, it's I-Movie I think. It's a free downloadable software for making Power Points as a movie that has a sound file. The sound file would be your podcast. You just drop the podcast into the Movie Maker software and then start adding slides and finally time the slides.
Also, I think it would make your podcasts more popular if you break them up into pieces so they're about 10-28 minutes, that's just a range that I can personally withstand during my busy life. Most times in the middle, about 15 minutes or so, is what I can regularly dedicate my time to on a daily basis. Two hours almost never works because at the very least I need a break and other pressing matters demand my attention on a daily basis.
So to keep "fans" coming back for more, what I notice by being a "fan" of other youtube figures, is that what they're teaching right at the moment has to be in a small enough chunk that I can take it in during the fast pace of my day. Then if I have time, I can go into their youtube channel and see specific subjects based on their titles, and catch up on more subjects I want to learn about. Anyway, I'm just thinking for the largest audiences at this point on the world wide web, your 10-28 minute range is the most "consumable," and that people like the
video aspect of shows, even if they're not watching that aspect. Like if they know you designed it so it can be watched or listened to, either with or without the video, and you kept the video down to pics that held for a long time, people would find that interesting enough to hold on for between 10-28 minutes per day or maybe at least five times a week. That's my max that I can put into one subject, So that's just one viewpoint!.