as any new feed in any site will get pounded during the first few days, even a week... id think a random sampling during the first 30 days, or an average of the first 30 days, would be the most fair for both sides...
Premium feeds that are regularly updated with hi-res, decent-length videos can cop a pounding with every new video release. Which is good for the person leasing the feed because it means that it's doing what it is supposed to be doing for your site. You are correct - the first month can be the most intense, however positioning within the site can have a major effect on the initial rush that you are referring to.