Before i choose the type of valve for my AVR, 4 years ago, I had the opportunity to meet a very nice lady that had a tissue valve for 7 years and then went thorugh a TAVR procedure, all went well, but that implant only worked for 4 years, so yes, how long they work for "IS" an issue, Industry is always trying to sale new products, that we all know; i also know a lady with a ball cage valve since 1980 and still ticking..... warfarin... yes, but... in the age of GMO and so many other things... i dont think Warfa is the boogieman , babayega or John Wick 4 , just a thought