Human Ages

A human life is brief in cosmic, geological or even historical terms but can be long in numbers of years, decades and personal or professional developmental stages. David Falkayn is seventeen as an apprentice on Ivanhoe and is forty-one nine years before the main action of Mirkheim. He is also eighteen years older than Coya who had been twenty-five in "Lodestar." At the end of Mirkheim, Falkayn becomes acting CEO of Nicholas van Rijn's Solar Spice & Liquors Company but, if he is by then fifty, then he is still has decades ahead of him in which to lead the colonization of Avalon, especially since sf can add artificial longevities, in this case antisenescence. 

Van Rijn is already old, thirty years older than Falkayn, when first seen whereas, in the case of Falkayn, as with Flandry, we are shown most of a career. Flandry has a Young Flandry Trilogy and The Trouble Twisters is a shorter "Young Falkayn" trilogy.