If I am understanding you right, I would just create a query based on the Last Communication time. If communication time is > whatever your ASCI, then they are not speaking to ePO.
Try Queries/McAfee groups - Agent management/Inactive Agents.
As I understand it, McAfee allows you to display only the total number of computers and laptops that are not addressed to the server for some time.
Inactive agent query will list the machine which are not communicated from 30 days. You can edit the query and under filter tab, select the time period as per your requirement.