Methods, computer program products and systems are disclosed for generating a planned time duration for a manufacturing process operation defined for planning purposes that includes an aggregation of multiple defined execution operations. Electronic information is received that specifies a production demand that requires use of the manufacturing process for fulfillment. A linear approximation is electronically generated of an overall time duration measure for the defined manufacturing process planning operation. The overall time duration measure is a sum of time components comprising at least a calculated measure for a variable time component for the longest of the multiple execution operations for the received production demand, and a fixed time duration measure for one send-ahead quantity for each of the multiple execution operations that is not the longest. The generated overall time duration measure is then returned.