The Laser Egg has been designed so that it doesn't need recalibration over time. The design of the airflow inside is optimized to reduce dust accumulation, the optics are all designed to last for over 30,000 hours, and the Laser Egg 2+ has an "economy mode" that is enabled when the device sits still for 15 minutes, at which point the measurement interval is adjusted, thus doubling the lifetime of the sensor. We've done all this so that the Eggs don't need recalibration, and they work well over the span of several years.
We put all the devices we develop through a series of lifetime tests, where they go through extreme conditions and incredibly high levels of pollution, so that we can be sure the sensors don't drift over time. If your Laser Egg has been exposed to extremely high concentrations of pollutants, you may want to blow some compressed air in the back, similar to how a keyboard can be cleaned, but you will not need to do anything more than that to maintain the accuracy of the sensors.