Require the controller to actually do something in the quiet periods ...
I'm not sure how many are actually aware that the FAA's rules
forbid a controller from doing anything not directly related to air traffic control. No books, magazines, browsing the internet, TV, cards to play solitare, commercial radio, personal phone calls... Nothing. Stare out the window at the runway lights, or at the sweep going around on the radar screen, that's ok.