Web based RSS readers store old feed items

At a recent UKeiG workshop on ‘Blogs, Wikis and RSS’ (April 22nd 2008), one of the participants noticed Google Reader was displaying very old items from one of her organisation’s RSS feeds. I suggested that the author of the feed had failed to delete them when updating the feed but When I checked our own UKeiG Events feed in Google Reader, deleted items going back to January 2007 where displayed. Had I also been guilty of not removing old feed items? I checked the code and the feed did indeed only have five items rather than the dozens suggested by Google. So it seems that Google Reader keeps old feed items and includes them in the list when you subscribe.

Bloglines behaves in a similar way and goes back even further (February 2006).  Newsgator also had some old items but only going back a month.