We always serve full historic RSS. If we didn't, there would be no way for most listeners to consume the old audio. When you use a third party service like mine, you either need to use the website that I provide for that back catalog (a bad experience for the listener) or jump through hoops to maintain a separate copy of each episode on your own website so it's still available if the feed is truncated. In neither world is that a decent experience for the content producer or the listener.