The lifetime is limited by the various components in the drive. If frequently overloaded, the gearhead components are subjected to more wear than under nominal load. In the case of commutator motors, these are the collectors and (carbon) brushes, and in the case of induction motors the bearings of the shaft. Extreme ambient and operating conditions cause a reduction in the lifetime guaranteed for operation under operating factor cB = 1.
For all gearheads from the ZEITLAUF standard program modular system, this is 5.000 hours (at operating factor cB = 1). (3000 hours in the case of mechanically commutated DC motors based on the motor lifetime!)