Honestly though, age shouldn't be that much of an issue for human heroes that reach a status like Balduran, as we do see other humans that are far beyond their natural lifespan appear in BG3 (Volo and Elminster). The real issue is that the Emperor is a really strange case where his associated time of disappearance and the assumed time of his return (likely inside of 100 years if not narrower) means he spent so many years just twiddling his thumbs in Baldur's Gate until Stelmane is born and old enough to become a member of the Knights of the Shield. Like one would think a relatively morally aligned (sometimes) mindflayer with the power to single handedly take down a dragon that is at least an adult (if not older) would do more in the setting.