What is the test for being diligent in pursuing a state habeas petition?

We readily acknowledge that we previously determined in Huizar v. Carey, 273 F.3d 1220, 1224 (9th Cir.2001), that a prisoner was diligent despite a longer delay. However, in Huizar, the prisoner engaged in a "steady stream of correspondence" with a non-responsive court. Id. The prisoner first contacted the court two months after he delivered his state habeas petition to prison officials. See id. Twenty-one months later, after receiving no response from the court, the prisoner had his sister mail a second copy of the petition by certified mail. See id. After five months more of waiting, the prisoner sent yet another letter to the court, his fourth mailing. See id. It was the prisoner's "steady stream of correspondence ... [that] show[ed] reasonable diligence on his part." Id.