I can't find any documentation on maximum number of active scheduled VM scans one can have in an account.
I am told you can have as many vm scans scheduled but only a max of 10 concurrent scans going at one time. The other scheduled scans will sit in a queued state until one of the original 10 finishes.
Qualys also offers a Continuous Monitoring | Qualys, Inc. application module.
See it in action: Continuous Scanning on Vimeo
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