iTunes will stop updating a podcast if you have not listened to at least one of its episodes in five days. This script will batch-update every podcast subscription so you don't have to manually update each one individually.
I have posted instructions on how to create a launchd agent to run this script automatically and invisibly in the background to ensure that your Podcasts are always updated.
Possible iTunes bug (July 17, 2014): iTunes 11 may still report a particular feed as not updating (with a "!") even though recent episodes have been downloaded via the script; you will have to manually tell iTunes to continue updating the feed by clicking the "!" button.
Remove iTunes tracks disassociated from files
Rename selected tracks' Song Names with their filenames (minus extension)
Copy Artist to Album Artist of selected tracks
Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
Correct song titles listed as "Artist - Song Name"
Exports and then re-imports selected tracks' artwork