Quarq power meters require no maintenance beyond basic cleaning and replacing the battery when needed.
If you are using a spindle based power meter or you have a spider based power meter that is on a firmware version older than 10, it is recommended that the power meter's zero offset be set regularly to ensure the highest level of accuracy.
More information about Zero Offset can be found below:
How to Set the Power Meter Zero Offset
What is a "Good" Zero Offset Number?