It also means it is not practical to have a Governor in every city and still have Generals available to command your armies. And though I'm not sure of this, I believe that if your City to Heir ratio is high (more cities than heirs) the game actually accelerates the speed at which heirs come of age (by fudging their age). Quite often I have taken a city, and the very next year, what would you know but a male heir has come of age. It seems to happens too often to simply be coincidence.

Honestly, I would prefer using MTW's governor and family mechanics. I liked that the family birth/death rates were independent of empire size, and that I could assign governors to any unit I want. I just don't see how the RTW mechanics are superior to the MTW one.