The way Pligg works, you aren't supposed to delete older articles just like a website wouldn't delete blog posts over a year old. For the purpose of
SEO it doesn't make sense to clean out posts after X days, but I can see why some people would want to remove stories in some circumstances. Right now, there is no way to mass delete stories without opening up some possible errors in the site. You could run a mysql command to clear out all stories so many days old, but I don't know if that will do a clean removal of everything. It would mess up the user post and vote counts and other things like that. Right now I suggest that you leave stories alone unless they are spam.