In view of the demographic changes, questions arise about the long-term development of the performance of work systems with an aging workforce. These questions are especially urgent if work systems with predominantly mental demands should be operated for many years. The simulation tool ESPE-AS can help to forecast the development of the performance of a work system with the given workforce for future periods. This paper describes a first approach of this simulation-based planning method and illustrates it using the routine activities for creating operations plans.