This is one of the settings where the ruler is pitting his children against each other in a bloody conflict, and the surviving one will inherit the throne. However, if you do have such a system for selecting the next ruler, you can forget about the thousand years of peace mentioned earlier. It will create rulers who believe that might makes right, the dead won't complain, and love or other gentle feelings are worthless. Such rulers would naturally look at the neighbouring countries and think nothing of crushing them.