A: Interval depends on speed, temperature and sealing: low-speed enclosed bearings may need grease every 1-2 years, high-speed motor bearings every 3-6 months; hot or contaminated duty needs more frequent service. Use lithium grease (e.g., NLGI 2) at ~30-50% of free cavity—overfill causes heat. Sealed (2RS/ZZ) bearings are usually maintenance-free and replaced at failure.