Ductwork systems should be rebalanced periodically to maintain optimal performance, as changes in occupancy, usage patterns, or system components can affect air flow rates and pressure losses. The frequency of rebalancing depends on the specific system and usage patterns, but it is generally recommended to rebalance ductwork systems every 5-10 years or when significant changes occur. Regular rebalancing ensures that the system operates efficiently, maintains indoor air quality, and reduces energy consumption.