My husband lived 29 years with double mechanical valves. He passed away recently at the age of 75 with his two mechanicals going strong until the last second. He passed away from other causes.
He was 44 when he had his AVR, and had a Bjork Shiley which was still in there, and never had to be replaced. By today's standards, this valve was big and clunky. The newer streamlined mechanicals are terrific, lighter, better bloodflow, much better dynamics. He had a St, Jude mitral mechanical too.
Joe was not supposed to live past 50 years old, but he fooled all his doctors.
You can live a very long full life. I know about this.