I personally believe that no two patients are alike. Some follow their dentist recommendations,others don't. Therefore even though an office may have certain policies regarding re makes, but those should be general guidelines. I have seen crowns placed 40 years ago and still good, others didn't last evens year. There are many factors that affect the long term longevity of crown such as caries risk, perio, poor hygiene.. etc

Therefore I don't think a 5 year warranty should be mandated.