The trouble is that even a wise and capable ruler sometimes picks a terrible successor. The most obvious example is the succession of Commodus after Aurelius —- Marcus was and is a widely read philosopher and admired leader, but his idiot son drove Rome into the ground.

The Yamato dynasty in Japan is the longest-lived political system on record, period. Historically, many emperors left governing to their subordinates; in some cases, there were even civil wars, but their longevity suggests an advantage to this approach.