A maintenance system for a process plant collects and uses historical data about maintenance orders. The data identifies the maintenance items for completing an order, such as the labor, materials, and maintenance tasks required. The data is historical data developed from actual completed maintenance orders. The system uses archived historical data and estimates various maintenance information, such as estimated cost for completing the maintenance order, and estimated start and completion times. The estimated data may be based on averaged data as a result. This estimated data along with the other maintenance order information may be sent to a scheduler for identifying a priority to the maintenance order and scheduling it accordingly.