c177ed05_Stepper_vs_Servo_Motors_Stepper_Vs__Servo_Motors_Stepper__Hybrid_
[Characteristics] Motor Life [Servo Motor (DC Brushed] The brushes on servo motors must be replaced every 2000 hours of operation. Also encoders may need replacing. [Stepper (Hybrid)] 
The bearing on stepper motors are the only wearing parts. That gives stepper motors a slight edge on life.
Stepper vs Servo Motors
Stepper (Hybrid)