If your PR person is good, they'll be knocking at your door looking for new angles or trying to expand the media list, or even trying new channels. If things aren't working, they'll tell you and ask for your help to find more interesting angles...
You don't get big muscles after just one workout and you can't expect big marketing results right away either. Lots of small business owners worry constantly about the ROI of their marketing investments. Instead, schedule time to review the results of what you're doing...