When cared for properly, porcelain veneers and Lumineers can last for a very long time (10 or even 20 years). On average, they probably last 8 to 15 years. Failures are typically caused by poor oral hygiene or failure to wear a night guard when one is recommended.   In most cases the word “failure” only represents that a new veneer must be made to replace the old one.   The tooth is usually fine though.