It depends on how often the patient uses it, and the intensity of stimulation required to relieve pain. The longer it is used and the stronger the intensity, the shorter the battery/generator life. This can be as short as 1 year or as long as 5 years. Fortunately, at this time batteries can be recharged. Rechargeable units will last longer depending on use. Most are approved by the FDA for 5 years or more. They would only need to be removed if they failed to recharge. After the battery/generator wears out it has to be replaced in the operating room in order for the device to continue to work. The leads, however, do not need to be replaced.