defrost heater replacement?

My side by side GE refrigerator is in need of a new defrost heater (Part no. AP2071523). This will be the fourth heater this freezer section has had in the seven years since the birth of this unit. I have replaced the timer and defrost thermostat as well in the past. Do they made a commercial grade heater available as I am about to part company with this unit do to this continuing problem. Is this a common problem with this design?