This depends primarily on a person's activity level. A tire on a car wears out in a shorter period of time when the car is driven many miles per day. Similarly , a younger patients typically wears out an artificial joint faster because of a higher level of physical activity. In general , a standard metal/plastic joint replacement in a person older than 65 usually lasts approximately 10-15 years. In a more active 40-50 year old patient , this type of replacement may only last 5-7 years. Fortunately , we now have metal/metal bearings (hips) that are able to tolerate 10-1000 times as much wear as the older metal/plastic bearings and therefore last much longer.