I have a very energetic granddaughter and if I matched her step for step I am afraid I would be dead in two days. I could not imagine trying to keep up with someone like her for 20 years. lol
Actually I think 45 might not be too old, but its marginal and it won't be entirely fair to the child. There may be much more money available, but there is a much higher probability that you will not live to see the kid graduate HS, let alone college . You would be surprised how many co-workers of mine died early, some even in their 30's,and certainly many more in their 50's. Some were the healthiest looking people I knew, lived a healthy lifestyle, but they had genetic defects (usually heart) that they never suspected. Two died of brain cancer very young.
I do think a child needs a good father around if possible, even though many fathers that are alive and kicking might be better off out of their children's lives, as many of you well know.
However,I would expect that most older men would have more tolerance, but probably not me. lol I would probably hang them up by their toes.(that was my favorite threat to my kids, now my daughter uses it. lol )
There is also a increased probability of the child having a genetic defect from either parent being older, but I do not know just how bad those odds are. (Downs,for example)