There are a few times that you might see an advertisment kick off even though it is disabled or set to run in the future, why is that?
Well lets say you set an advertisment to run 3 months in the future and all machines pick it up. A month later a machine is turned off and remains off. The admin discovers a problem and disables the adv or sets the date even farther into the future. When the machine is finally turned on it might not pick up the policy in time to stop and it could kick off. Is this a common occurance, no. It is just a split second decision that the client makes and it chooses wrong. We typically see it with adv that are set to ASAP with no user logged in. The client will execute what it knows to be the correct order until the new policy is retrieved.