Service Interval for Wheel Bearings

I ride between 1,500 and 2,500 miles a year in mostly dry conditions, including winters. How often should I check the wheel bearings...or should I say is there any thinking on a service interval for their replacement?

These are Trek Select wheels.

Thanks.
Mark

Once every 12 to 18 months. But take the wheels off, skewers out and spin the axle with your fingers. Crunchy-OVH, smooth, not.