Ok...I see now....when you send a temp attack and then cancel it, they have to come back as far as they went, so even though you have 90 seconds to cancel it, if you cancel ii 30 seconds after they go, it ill take 30 seconds to get back and then the time it takes to send them again, so you are over 30 seconds behind your quarry.
So to do this right, I guess you have to send the trips out within a couple seconds before they get there, cancel it and wait the couple seconds for them to get back, and send them out again immediately so that you are right on thier heels. I wonder what the target time for something like that is...2 seconds? 1 second? I think I could swing 5 seconds right now, but I'd hate to get caught with being tooslow and long troops because I cut it too close.