Shorter interval is needed when the website has lots of content changes (ex. Intranet). Then, recycle bin gets full quickly and can't be delete manually due to a timeout nor through a scheduled job, due to the long interval.
When I disassembled the code, I saw that it has a const: DateTime.Now.AddDays(-30.0) in EmptyWastebasketJob. Could you make the number of days configurable?
(As a workaround, I made my own scheduled job doing exactly the same as the built-in one except reading from AppSettings).
Seems reasonable enough :) will see if we can include that in a minor release.