Good for you for getting the treatment you need. The goal of any good dentist is to get a crown to last as long as possible. They usually brag about how they have had a crown last 30 years. This is certainly the exception but it is not unobtainable. Insurance companies will usually pay to replace a crown every 5-10 years depending on the plan and company.
Crowns can fail in a couple different ways. First, depending what the crown is made out of, the porcelain can chip off. While this is not an immediate problem it can cause a gap between your teeth which traps food. While this is annoying it also usually causes a cavity below the crown. Secondly, crowns fail because of a cavity. Crowns cover the tooth and the crown itself does not decay; however, there is always an edge where the crown meets the tooth, and this is where a cavity can form.
If either of these happen, you usually need to replace the crown. Hope this helps.
My best to you!
William F. Scott IV, DMD