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.
Display, create text file listing info of dead tracks
Copy Artist folder, Album folder and file names to appropriate tags
Remove iTunes tracks disassociated from files
Append user-entered text to beginning or ending of selected tag of each selected track
Perform search-and-replace on text in your choice of tags
Select iPod tracks in iTunes and add them to iTunes