Obligatory warning: This script has been designated as an obsoleted "Retro Script". There is no guarantee that it will function as described with modern versions of iTunes and/or macOS. If used in its current form it may not work at all without modification and, at worst, it may 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.
downloaded 55m 3s ago
Enter text for the selected tracks' Category tag
downloaded 1h 19m 16s ago
Perform tasks on a batch of playlists; rename, delete, duplicate, merge, more
downloaded 1h 42m 43s ago
Drag-and-drop to convert audio files with iTunes
downloaded 2h 26m 58s ago
Displays files in iTunes Media folder not in iTunes track library
downloaded 2h 27m 12s ago
Convert selected tracks and export the converted files to a new folder
downloaded 3h 0m 3s ago
Remove iTunes tracks disassociated from files