The longevity of fillings in teeth depends on various factors such as the type of filling material used, the location of the filling, oral hygiene practices, diet, and the amount of wear and tear the teeth experience. Generally, amalgam fillings (made of a mixture of metals) tend to last longer than composite fillings (made of a tooth-colored resin). Amalgam fillings can last for 10-15 years or more, while composite fillings typically last around 5-10 years. However, advancements in dental materials and techniques may improve the durability of both types of fillings.