Well, the good news is, barring testicular injury, wrong kind of
   food/medicine wrecking it or some sperm issue, you can procreate
   at nearly any point in life* so at least you don't have the time
   factor to worry about. Maybe your energy level won't be quite so
   high if you have your first kid at 60 or 70, but it's not
   uncommon, so long as the mother is in good-egg age.