Best Answer:  For most people, they can easily last 10 years. Most people need fillings replaced b/c their oral hygiene/diet is not good enough and a new cavity develops around the filling, this can happen in as little as 6 months. If you chew a lot of hard things, like ice or grind or clench your teeth, this can wear these fillings much faster than silver/amalgam fillings and break them down within 3-5 years. Amalgam fillings hold up much better to large amounts of pressure from grinding and chewing ice.