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.
Add or subtract a user-entered number from each selected track's Plays
Apply selected CD's CD Text to its disc and track tags
Export artwork of selected tracks to parent or specified folder
Sort purchased tracks into discrete playlists by name or account ID
Set the Album Rating for the album of a selected track to full- and half-stars or computed clear-stars
Remove iTunes tracks disassociated from files