Porcelain veneers last 10 years on average, but with proper care can last for much longer (even 20 years).
Some factors that contribute to a longer porcelain veneer lifespan include basic hygiene like flossing and brushing, wearing a mouthguard if you play a contact sport, wearing a nightguard if you grind your teeth at night, and avoiding extremely hard foods like rock candy or ice, and avoiding smoking.