I have added the 5by5 master audio feed to the list of feeds supported by 5by5 Time Machine. And unlike the feed offered on 5by5.tv, the feed offered on 5by5 Time Machine contains every single 5by5 episode currently available - 2137, as of this post.
Of course, with all these episodes, the amount of data that must be downloaded by the podcast client on every refresh is quite large (~7.5MB). Because of this I have also added a parameter, limit, that you can use to limit the number of episodes returned by the feed to a certain number, always the most recent. This can be used like so:
The above link will return the most recent 50 episodes from the master feed that has been time-shifted by 456 days. If you subscribe to this link, as new episodes get added old ones get moved off the end.