I'd like to be able to set a maximum number of items per feed.

In other words, if I include two feeds, one of which has new posts 5 times a day, and the other once every two weeks, the former feed will dominate my site, which isn't what I want. I'd like to be able to set a maximum number of items per feed, which would trigger the automatic deletion of any posts in excess of that limit when new posts are added.I'd be happy to contribute to the implementation of this, if someone could give me some pointers on how it might be accomplished.