It should be possible to control the number of items included in a feed independently of the number of items included on the page (the latter, however, possibly setting an upper limit). This would be particularly useful on archive pages providing a feed. Presently the feed grows huge, if the archive page has no limit on the entries listed on it (as in the list of all entries in the Ion FAQ). An alternative useful filter would be filtering by the age of the page.

Done, option name is feedshow --Joey