Obligatory warning: This script has been designated as a "Retro Script" and there is no guarantee that it will function as described with modern versions of iTunes and OS X and may even corrupt or destroy data.
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): Looks like the iTunes AppleScript command updatePodcast command is broken as of iTunes 11.
Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
Exports and then re-imports selected tracks' artwork
Apply selected CD's CD Text to its disc and track tags
Locates pairs of track entries pointing to the same file
Append user-entered text to beginning or ending of selected tag of each selected track
Batch merge and/or delete playlists