Hard question.
At first what do you call optimal age? The biological maximum determined by our biology and genetics? We are near to it. Or the plausible age determined by our medical science? We can increase this one, and i don't think its a bad idea especially in west where the population is decreases, what means we need to extend our lifespan and productive age, because sure as hell our way of life not makes possible the drastic increase of fertility, and anyone who comes there are either became the part of it, and get himself caught in the net of same problems.
or how can i put it nicely?
Well? I'm afraid there is no way to be politically correct. A threat to our society, with a high factor of risk to change our civilization. Now... The question is, they can change it for the better, or worst?
I'm afraid the second answer is the right one, because compared in sociological advancement? They are behind us. Science and tech? the gap is insignificant in there, nothing they can't learn.
Furthermore i think this question is cannot be separated from the current world politics, and social crisis es. They are part of it trough the problems created by our declining population, what i don't see as necessarily bad thing. Because there are too many of us already, the reason why is a problem, because in the other parts of world the population is not declining, so we cant keep up, and even worst by the aging of population we also facing with another disadvantage.
In short, there is no way around it but we must increase our lifespan and productive age, and bypass, resolve the problems causing infertility. Poisons, unhealthy life, and such.