Scott,
The scan in 6.4 is a snmp scan and the interval is on the cluster-wide settings [default-24-hours, minimum of 6-hours].... we should post a message ot the event-log when this runs from memory....
In 6.5 we are adding a lot more scanning options.... again hope some of this helps.....
We can add multiple snmp community-strings to check, previously it was only public.... now we can add as many as required and specific their type V2,V2c,V3 etc.
We will also