A method includes determining a first measure of a benefit of disallowing transmission during a time period within a time frame. The benefit of disallowing transmission includes an immediate benefit of disallowing transmission during the time period, and a future benefit of having, for use in a subsequent portion of the time frame, a decremented number of opportunities to disallow transmission. The method also includes determining a second measure of a benefit of not disallowing transmission during the time period. The benefit of not disallowing transmission includes an immediate benefit of not disallowing transmission during the time period, and a future benefit of having, for use in the subsequent portion of the time frame, a non-decremented number of opportunities to disallow transmission. The method also includes determining whether to disallow transmission during the time period at least in part by comparing the first measure to the second measure.