Welcome! Valve choice is always a tough one. At 66 a tissue valve could last you the rest of your life, but if it needs replacing, you would be at an age where surgery (or however they are replacing tissue when the time comes) could be risky.
Getting a mechanical doesn't guarantee you that you won't have another surgery. But at 66, if everything goes normally, you most likely would not have to have another one.
I've had my St. Jude mechanical for almost 15 years. I was 32 at the time it was put in. I only hear the clicking at night sometimes, or if I'm in a small tiled bathroom. As 901 says - I'd be bothered if I didn't hear it!!!
Taking Coumadin is not the nightmare life that some would lead you to think. You eat what you want, drink what you want, pretty much do what you want, and let your dose be adjust to that. We have, in my opinion, the world's best resource for Coumadin information in our member Al Lodwick. I would recommend going to his site and doing some reading.
www.warfarinfo.com
I would have to say that if I were 66, and it was my first surgery, that I would lean towards choosing a tissue valve. With a second surgery, I would be as confused as you are.
This is just a suggestion - after doing some research here and on Al's site, I would pick a valve and then talk with the surgeon about a game plan. If you are leaning towards tissue, I would ask the surgeon to assess the scar tissue and other factors once he gets "in there" and make a professional judgement based on what he felt would be present for another surgery in, say, 20 years. If he's already seeing lots of scar tissue from your surgery 4 years ago, I'd (personally) choose mechanical. If he's not seeing much scar tissue and (other than a failed repair) an otherwise overall healthy heart and overall total health, I'd choose tissue. But these are just my thoughts based on what I know now.
You have options - the only wrong decision is to not have anything done.
Best wishes!