There are basically two parameters which can influence the calibration of a cup anemometer: the geometry and the bearing friction. Assuming that the geometry, and hence the aerodynamics, is constant over the lifetime of an anemometer the critical parameter is bearing friction.

Bearing friction may among others be affected by lightning, mechanical impact, wear and corrosion. By design, WindSensor anemometers are tolerant of lightning due to the non-conducting property of the cup rotor, which tends to direct the lightning current along the surface to the body of the anemometer rather than through the bearings. Furthermore, the bearings utilize a special steel type which is several times more resistant to wear and corrosion than steel types otherwise used in the industry. Combined with the most durable lubrication in the industry WindSensor anemometers have proven to operate in excess of 10 years under ideal conditions.

However, as cup anemometers are operated worldwide under different conditions in all types of environment it is not possible to specify rigid service intervals.

We specify a service interval of 1 to 2 years depending on the operating conditions. For example, it is common practice to replace cup anemometers on offshore towers at 1-year intervals due to the extremely high costs of accessing the site. We recommend that our customers should define a maximum service interval depending on the conditions on the specific site.

However, given the risk that instruments might be damaged by handling already during the installation or at any time after installation for example by static discharges and falling ice etc., the most important precaution in operating a meteorological tower is to continuously monitor the performance by correlating measurements from two identical anemometers installed at the same level as well as correlating measurements from identical anemometers installed at different levels.
    
It cannot be justified deploying different models of anemometers on a meteorological tower as different types of anemometers have different responses to air temperature, air density, inflow angle and turbulence resulting in different measurements, even if installed at the same level.