Not to stray too far afield here, but "the suffering from the consequences of the parents wrongdoing" goes to the third or fourth generation for a specific reason, and it is not "hard to understand why it can go on that long " at all. Simply put, that is how long someone is apt to live to see his progeny. Three or four generations of his descendants are made to suffer in order to punish him, just so that he will wail every day of his potentially long life at the visible consequences of his sin. (Aquinas saw this. “The text adds, ‘to the third and fourth generation,’ because men are wont to live long enough to see the third and fourth generation.” Summa Theologica Part II Q. 87 Art. 8.) The framework of three or four generations is specifically picked so that the perpetrator would not live to see an unpunished descendant.