From what I've read, the older a man gets, the percentage chance of him fathering a child with a birth defect rises significantly. However, that's kinda deceiving. The analogy in the study equated it to buying 2 lottery tickets instead of 1. You're probably still not going to win (or lose in this case).
My wife and I wanted a lot of children. We tried for 7 years to get the first one and 5 more to get the 2nd one. Some people started telling us we should stop trying because the chance of birth defects had doubled at our age. Our Doctors said to keep trying because the chances were very low to begin with, and remained low even though they doubled percentage-wise.
So, we figured we'd get one and if it was OK, we'd try for a 2nd. If not, we'd deal with the first one, as we were mature enough to handle anything thrown at us.
We were fortunate to get two healthy babies out of the deal.

We also lost a few in miscarriages.
So our hearts go out to the folks that want children and are having a tough time conceiving. We were at the point of adoption when the last one came. We just knew that we wanted children, and had a lot to offer.
Would I want to father more babies at age 50+? Now, no. But if I didn't have any already, probably yes.
Depends on the woman, my health, her health, financial situation, the desire to procreate... lots of factors, I'd assume.