Question
You want to create a filter that automatically populates with machines that haven't sent a configuration is a specific amount of days.

Answer
Create a filter and use this query:

SELECT * from vComputer vc

JOIN (
select ResourceGuid, LastConfig = datediff(dd,MAX([StartTime]),getdate()),
LastConfigDate = MAX([StartTime]) from Evt_NS_Client_Config_Request group by ResourceGuid HAVING datediff(dd,MAX([StartTime]),getdate()) >= 1
) as a on a.ResourceGuid = vc.Guid

ORDER BY LastConfig

The value for 'datediff(dd,MAX([StartTime]),getdate()) >=' can be changed to any amount of days desired.  In this example, the filter will report all machines that have not sent a configuration in 1 day.