I have just uploaded to the WordPress Extend Plugins repository the latest version of my free plugin BNS SMF Feeds. The recent update adds a new option to better control the Feed Refresh frequency. Here is the changelog:

== Changelog ==
= 1.2 =
* added feed refresh frequency (in seconds) option
* added new screenshot of option panel

… and here is a screen capture of the most recent control panel:

BNS SMF Feeds Control Panel from version 1.2