Sorry to jump in late, and I'm not questioning your and your wife's decision not to have children, but I wanted to give my answer to your "genetic make-up" question.
I wrestled with the same issue as I have allergies and two chronic illnesses. Did I want to pass along (if the illnesses are inherited) these diseases? But then I realized that even though there are times that I am miserable, and I may end up on the left side of the life-expentency curve, I am very happy to be alive!
So we took the plunge and I have a wonderful (although challenging!) two year-old son, and he's the best thing that has ever happened to me.
Again, I must state that expected longevity was only one of my criteria, and not the most important one at that.
I did want to retire, though, so I factored it in.