I don't see any cpu over usage with the script. Processing rss take some cpu, but it should be much less when compared to converting a video.

To set cronjob, see

http://www.buyscripts.in/youtube-video- ... ation.html

Clean up cache files

1. Run remove_xml_cache.php. For security reason, you may rename it to other name like remove_xml_cache_secretword.php
2. As an optional, you may set cron job to run this script.

0 0 * * * GET http://www.yourdomain.extn/remove_xml_cache.php > /dev/null