The procedure of placing veneers is often an irreversible process because a thin layer of tooth enamel is removed to fit the shell when it is placed; this lack of enamel would otherwise leave the teeth vulnerable to decay, wear and tear, and sensitivity to temperatures. The life of a set of veneers depends on the material, as well as oral hygiene and lifestyle factors. On average, porcelain veneers last around 25 years; composite veneers have longevity closer to seven to 10 years. Whereas porcelain veneers are more likely to need replacing when damaged or compromised, composite veneers can be touched up and easily fixed, despite their shorter lifespan.