Indeed it is true that Google Reader caches the items and it is NOT possible to paginate on RSS2, RSS or Atom feeds (unless they have rel=next link, which none of them seem to have).
However, we can leverage the existing Google Reader infrastructure, with some work, to retrieve a list of, say 200 items!
Given the above podcast url we retrieve the latest 200 episodes by:
- Using the ...google.ca/reader/atom/feed prefix instead of the usual view/feed as can be seen in your google reader.
- Appending n=200 as the query parameter.
So we have:
http://www.google.ca/reader/atom/feed/http://leoville.tv/podcasts/sn.xml?hl=en&n=200
There is a very insightful reverse-engineered google-reader API project located at http://code.google.com/p/pyrfeed/wiki/GoogleReaderAPI