I realized after reading the WHMCS documentation that the cron.php should be run once per day and not every hour on the 5th minute. Out of the box using the Install Scripts for WHMCS 4.5.1 it would appear that the cron.php cron job is setup to kick off hourly on the 5th minute. I think this should be changed to kick off at 9:00am by default. (Perhaps this is on purpose for testing??)
Here are the notes on the Automation settings for WHMCS:#
To enable the automation features to run, make sure you set up a cron job to run once per day at the time you want invoices to be sent out and accounts suspended (eg. 9am).
php -q /home/xtremeservices.net/public_html/billing/admin/cron.php OR GET http://www.xtremeservices.net/billing/admin/cron.php#