The length of time can vary based on several factors, such as if you grind or clench your teeth. But on an average, you can expect a metal filling to last for about 15 years Old fillings which consisted of mercury should be replaced since presence of mercury can have a negative impact on health. With new composite resin fillings which are made of tooth-colored material & are safe. I would recommend you to visit Smile LA for more information https://smilela.com/