A few days ago I posted on how to use AutoArchive in Outlook 2007 to help manage the size impact of your RSS Feeds on your Exchange mailbox. One of the downsides to using AutoArchive is that there is no easy way to apply a defined set of parameters to a number of RSS Feed folders at once – folders can either use the global setting or they need to have their parameters set individually.
Here's a trick that I use to workaround that limitation and keep my RSS feeds down, along with archiving the content should I ever need to find it with Outlook 2007's Instant Search (plug plug).
This will archive all of the RSS Feed items out of your default store that are older than the set date, and move them into the .PST file you created. This one-off run of AutoArchive does not change any of the settings you may have on the individual feed folders, it's just a quick way to get RSS Feed items out of your Exchange store. You can run it whenever you need, just follow the steps above (minus creating the new PST).
You've reduced the amount of RSS Feed items in your default store while retaining them in an archive PST – sweet!