Refrigeration systems should be recommissioned periodically to ensure that they continue to operate safely, efficiently, and reliably. The frequency of recommissioning depends on various factors, including system type, usage, and maintenance history. As a general rule, systems should be recommissioned every 5-10 years, or when significant changes are made to the system or its operation. Recommissioning can help to identify and address any issues that may have developed over time, and ensure that the system continues to meet its design intent and performance criteria.