Tidbit from the Korban HaEdah to Yerushalmi Sotah 33a

The Yerushalmi states that in Yavneh, the Sanhedrin at the end of the Second Temple period asked Hashem to exempt them from the responsibility on Nistaros that Yehoshua had compelled the nation to take when they crossed the Yarden. The KhE posits that this took place when the Sanhedrin went into Galus 40 years before the Churban. Accordingly, when R' Yochanan ben Zakkai says to Vespasian: "Tein li Yavneh v'chachameha," he is referring to the Sanhedrin that had already been there for years.