
u/TsarOfIrony — 18 hours ago

Rather than having one khagan who reigned for the rest of his life, the Khazars had a system of dual leadership rooted in Turkic and Jewish tradition. The greater khagan was recruited from the Khazar house of notables and nearly strangled until he declared the number of years he wanted to reign, at the expiration of which he would be ritually killed by the nobles.
Arab traveller Ahmad ibn Fadlan wrote that there was a maximum limit on the number of years of a khagan's reign. If he reigned for over 40 years, the Khazars felt he was too old to rule, and executed him.
Sources: