I recently committed the following change to the Development Version of FeedWordPress:
Update Scheduling: improvements to handling of feed-requested update scheduling. Include a time-staggering fudge factor for all update schedules, including feed-requested ones. If a user sets a longer interval between updates than is requested by the feed, user can choose whether to speed up at feed's request, or to stick to FWP's normal schedule.
This change will be part of the next public release of FeedWordPress. Interested? Curious? You can check out the details at the WordPress plugin repository ...