Using Devonthink for RSS

I am using Devonthink for RSS feeds which seems to work well for me. However the feeds seems to stay forever. How can I get them to automatically delete after a week.

Menu bar > DEVONThink Pro Office > Preferences > RSS > “Remove articles”.
That’s a dropdown menu with different options. ‘After one week’ is also offered.

With the impending demise of Google’s RSS reader I suspect many DT users will start using DevonThink for RSS feeds. Is there a way to display a count of unread RSS items in the DevonThink dock icon like unread e-mails (you would of course need to be able to turn it off). Just a thought!