Cleaning efficiency meter accessories should be replaced based on several factors, including the manufacturer's recommendations, the frequency of use, the environment in which they are used, and the specific type of accessory. Generally, manufacturers provide guidelines on the expected lifespan of their products, which can range from a few months to a couple of years. 
For accessories that are used frequently or in harsh environments, such as those exposed to high levels of dust, moisture, or chemicals, more frequent replacement may be necessary. Regular inspection for wear and tear, such as cracks, corrosion, or reduced performance, can also help determine when replacement is needed. 
In some cases, accessories may need to be replaced after a certain number of cleaning cycles or operational hours. Keeping a maintenance log can help track usage and ensure timely replacement. 
Ultimately, adhering to a proactive maintenance schedule and replacing accessories before they fail can help maintain optimal cleaning efficiency and prevent potential damage to the meter or inaccuracies in readings.