AVR Life Expectancy

Hi,
I had my arotic valve replaced with a St. Judes mechanical valve just over two years ago. At the time I was 23 and thought that, with the exception of having to take anti-coagulants, my life would return to normal and I could look forward to a happy future. Recently, however, despite feeling good and well, I have started to worry about how this will effect my long term future and life expectancy. Most studies I have found on the internet seem to suggest that having this type of surgery at a young age has a detrimental effect on patient life span. However, other studies are more positive. I guess I'm just looking for an actual answer as to how avr in young adults effects their life expectancy?
Thanks & best wishes.