When you subscribe to a podcast in iTunes it only lists the 10 most recent podcasts. Is there a way to get the older podcasts?
As far as I remember you can add them "manually" by clicking on the list. Just search for the show on the iTunes and click on the individual shows you want to download.
Edit: it seems that the iTunes store just shows episodes of the certain period.
From Apple's Support - Podcasting Frequently Asked Questions (FAQ):
I subscribed to a podcast, but I don't see all the episodes—only the latest. How come? iTunes will only display the podcast episodes that are included in the podcast feed. Many podcasts have the older episodes archived on the web. Check the podcast hosting site to see if older episodes are available.
If the reason the podcast is missing episodes is because they’re missing from its feed, and the feed has history archived in the Wayback Machine (which many are), you can use Backfeed1 to generate a feed which includes all current and historical episodes2.
1. Disclaimer: I created Backfeed, since I was annoyed at the same problem.
2. Backfeed depends on snapshots of the feed existing in archive.org. The results will be limited by the number of snapshots available for retrieval by a sane number of API requests.
Many Podcasts have their own website as well. If you can find the website, then they likely have an RSS Feed that you can add into itunes rather than the link from iTunes store. In most cases this will get you the older podcasts.
Updated: Also some podcasts will have enchanced versions of their podcasts with pictures/video or alternate feeds where maybe a subset of the podcasts is of interest. Manager-Tools is a good example. Itunes only shows a subset of the episodes. Their website has an RSS feed with all of the episodes, and a "Basics" feed with a subset of the episodes that deliver the core of their philsophy.
Here's a way to do it right from the podcasts section of your library: right-click/secondary click on the podcast and select "Show all available episodes". It will list all of the previous episodes. From there, you can click "get" to download separate episodes, or "get all" to download all of the episodes.