If my understanding is correct, then (last command times of client) should have a value other than < none > as long as the client has received a UDP notification at some point, which should happen very regularly, unless all operators with management rights never use the console to do much of anything.
In this post, @AlanM suggests that the relevance will return none if the client is restarted, but then suggests that is not the case and that it should behave the way I described above.
This is meant to be taken as a policy action to Automatically enable Command Polling on clients that have not received UDP commands/notifications.
You can check the logs for UDP commands: http://bigfix.me/analysis/details/2994616
number of lines whose(it contains "GatherHashMV command received" OR it contains "DownloadPing command received" OR it contains "ForceRefresh command received") of files whose((name of it ends with ".log" OR name of it ends with ".bkg") AND exists lines of it) of folder "__BESData\__Global\Logs" of parent folder of client