The frequency of adjustments to the supply temperature set-point in district heating networks influences the overall operating cost in two ways: adaptability to changes in network conditions; and availability of time for determining an appropriate response. In this paper we investigate this trade-off and show that operating costs can be reduced through appropriate control period selection. Eleven hypothetical scenarios spanning five different networks have been simulated under a variety of control policies. When compared to a constant supply temperature strategy, the best policy in each case achieved a loss reduction of 5-24%. (C) 2010 Elsevier B.V. All rights reserved.