You might find this discussion/information useful.
http://moodle.org/mod/forum/discuss.php?d=5179#23659
Another Health
warning : some webhosting providers can become upset when cron jobs are executed every five minutes. No kidding....Typical 'warning' even from a normally friendly hosting provider .....
" DO NOT ABUSE this feature. In the event that we determine that you are abusing the system from your use of this feature, it will be disabled permanently for your account. If you know how to use Crontab, then you are quite aware of the drain that this feature can cause on server resources. Precautions that you should take are:
Limit the number of processes that you run.
Do not run processes every minute.
Schedule your processes to run at low activity times. "