It's always been my feeling that God lends you your children until they're about eighteen years old. If you haven't made your points with them by then, it's too late.
Bio: Marcus Aurelius was Roman Emperor from 161 to 180. He ruled with Lucius Verus as co-emperor from 161 until Verus' death in 169. Marcus Aurelius was the last of the so-called Five Good Emperors.