If I haven't addressed it prior to this point in the game, I'm not gonna screw someone at this point either.
One thing I'll normally do is when the 15s warning sounds, as I walk toward the huddle to remind them to finish it up, I'll give a quick short blast on my whistle. If I've noticed a team is normally slow to break up, I'll try to position myself near the head coach so that if the buzzer sounds to end the time out, I'm blowing my whistle again, and this time, the coach's ear is probably gonna ring for a couple seconds afterward.