Hi Jeannie,I would really depend on how often you need to update the RSS pheeds, and how many pheeds need to be updated.
The actual updating is pretty much the same as a "hit" from a visitor. Updating 12 different actions every hour shouldn't be a problem.
It would also depend on how much traffic each page was getting. This would probably be a bigger drain of server resources since the pages are dynamically generated, however we should assume that if a page is getting traffic, it should generate more profit than the cost of hosting.