New discoveries have found exceptions to Mendel's basic laws, but none of Mendel's things have been proven to be flat-out wrong. Hail to the Father of Genetics ! The name is ma-ma-ma-ma-ma-Mendel.
Dental crowns should last on average from 10 to 20 years. Crowns are still subject to fracture and cavities, so it is important to take extra care in brushing and flossing around crowned teeth to prevent them from needing replacement too often.
How long dental crowns will last depends on many other factors in addition to the material they are made of. Practicing good dental hygiene by brushing and flossing twice a day will increase the life of your crowns. You can also increase crown life by limiting consumption of hard or crunchy foods.