I had a 5.2 ascending aortic aneurysm with a bicuspid valve, my aneurysm was repaired 5 years ago. Before the surgery my surgeon told me that he would look at the valve if it was highly functional he would leave it as my natural and working bicuspid valve was better than any artificial valve he could use, he would have a pig valve ready just in case.

He left the valve, my cardiologist who is an aortic disease specialist, monitors it every year with an Echo and measures the degree of stenosis. 5 years later it is still in good shape. Eventually when it needs replacement it can be done endovascularly since the aneurysm is repaired, they would not do it if the aneurysm was there (risk of rupture)

That procedure is relatively simple, my mother got it done last year at 88yo without any issues.

I was (still am) very active and in great shape, taking care of your body pays dividends, my surgeon gave me almost 100% chance of no issues during surgery and that was the case, it went very smoothly and I was back to work in 3 weeks. Exercise also slows down the deterioration of the valve.

Your son in law will be fine!!