RSSRadio has a few things which work differently from other Podcast apps, this article describes these.
RSSRadio plays back podcasts from the Playf Queue. This is a completely flexible list to which you can add shows, remove shows and put into any order you like.
Although RSSRadio has things called "Playlists" you still move these shows (either the whole list, or just individual shows) into the play queue for playback, you don't play them directly.
Some Podcasts have a lot of shows, and some have a theoretically unlimited amount of shows depending how long you have been subscribed to them.
In order to keep your Podcast show lists to a sensible length, and to help with app performance, RSSRadio has a concept called "Archiving".
Generally speaking archived shows are shows that you are finished with, and are not likely to listen to again. Sure you can get them back if you have to but they are out of the way.
Archiving is controlled by either 1) Manually choosing to archive a show or 2) The 'Archive Older Than' subscription setting.
Auto Deleting Old Shows
RSSRadio only runs the rules to delete old shows (and archive them, and apply any number of settings) when it refreshes a podcast, so don't sit there staring at a just listened show waiting for it to happen - it will just let it be. This is handy as it gives you a chance to put it back in the play queue if you wanted to listen again.
Oh, and the Play Queue is sacred. Shows still in the Play Queue won't get auto deleted, auto archived, or auto anything...
When you subscribe to a podcast you choose to either take the default settings, or some specific ones. Don't go into the default settings later and think its changing all your existing podcasts, its not!