When you add a podcast, then you add teachings to that podcast.
audiopodcast1.xml will include teaching1.mp3, teaching2.mp3, teaching3.mp3 (you add them to the podcast in the media file record)
If you create another podcast it might be videopodcast1.xml and have teaching1.wmv, teaching2.wmv, teaching3.wmv.
it's up to you about how you want to structure them, but we have only two xml files - two podcasts - but numerous teachings connected to each one of them. It's a good idea to have few podcasts because people have to subscribe to them and you want to make it easy and simple. If they keep having to resubscribe to new podcasts you might lose listeners.
Does this help you?
Tom