Podcast apps tend to save everything for some stupid reason. My iPhone was full and I noticed Overcast had saved like 3 GB of old episodes. Pretty terrible UX.
Start caching the stuff you obviously don't want to re-fetch over HTTP every single time the user scrolls around in their timeline, and 100MB is a pretty reasonable footprint.
Similarly, when you transfer to a new phone or restore, it won't take those files with the backup, and if you have a bunch of files still around, it'll re-download those, taking several hours or days.