I'm not totally on board with this.

Natural tissue valves (pig or cow) usually last 10-15 years. Sometimes less, sometimes more. If you need a valve replaced, or in my case repaired, but if the repair doesn't work, you have a option to get a mechanical valve or a animal valve. Depending on your age you may decide on a natural valve over a mechanical. I had my mitral valve repaired but I had to decide which valve I wanted in case the repair did not work. I chose the tissue valve because it is quiet and you don't have to take anti coagulant drugs for the rest of your life. At 65 if the valve only lasted 10 years, the Dr. assured me that they would be able to replace it through the groin vein as a fairly simple surgery. "we are that close" were his exact words. My repair worked and I am on a baby aspirin a day and Metoprolol to slow my heart rate down.