As far as how long do well-made porcelain crowns on your front teeth last, that will vary depending on many variables which include:
Oral hygiene (brushing and flossing habits)
Systemic health issues such as diabetes that may weaken your overall dental health
Frequency of preventative care visits
Your bite and chewing force
Condition of your adjacent teeth—the healthier the better
Healthy dietary habits
Dry mouth conditions caused by certain medications that may cause teeth degradation
On a more optimal note, porcelain crowns have the potential to last a life time. After all, the materials that make up porcelain crowns do not decay. As such, the life time of your porcelain crowns is dependent on how they are cared for, professionally maintained and treated over time. The most critical problem you may have with your porcelain crowns that affects life span is the oral hygiene. Proper brushing and flossing is key to protecting gums and bone surrounding crowns from degradation and decay that sets in along the teeth edge which sits against the crown. Besides, you cannot be too rough on your teeth with porcelain crowns by chewing ice and hard things. And you cannot be using your teeth as tool for opening bottle caps, holding hard objects, or biting finger nails.
When you have a well-fabricated porcelain crown with design of the prepared teeth having proper thickness of porcelain to maintain strength, having a well-sealed margin between your crowns and teeth, and that your crowns are correctly adjusted to the bite and chewing forces, you are guaranteed a longer life time for your crowns. In other words, you have within an average life time of 10 to 25 years for you to need replacement of your crowns due to wear and tear or aesthetic changes to your surrounding teeth, or maybe not. Most insurance companies will pay for crown restoration after 5 years. A well-made crown should not have any defects that need replacement before 5 years.
Strength of your porcelain crowns is only one of the variables that determines the longevity of your crown; careful preparation of your crowns by an experienced dentist with the collaboration of a skilled ceramist who fabricates the crown, as well as proper oral hygiene and preventative care should give you the best long term results for your porcelain crowns on your front teeth. So in general, porcelain crowns are remarkably durable and can maintain shape and function for many years. A crown manufactured to the highest standards, properly fitted to your bite and well cared for, can therefore potentially last a life time.