The full model posits two cycles, one of which involves these "fathers-and-sons" cycles, because there are deep underlying problems. One generation tries to so

The full model posits two cycles, one of which involves these "fathers-and-sons" cycles, because there are deep underlying problems. One generation tries to solve them, violently, the next generation abhors revolution enough to not do that. However, eventually you get an actual success at fixing the underlying problems (often related to elites accumulating too big a percentage of the resources), then the "fathers-and-sons" cycles stop because there's not a big well of repressed anger for counter-elites (Robespierre, Cromwell, Lenin, etc.) to draw on. So, for each country, it will not always be a two-generation cycle because it depends on whether you have the intra-elite competition, fueled by an ever-increasing concentration of power at the very top, which causes the disaffected masses to have a counter-elite to follow down the path of upheaval.