What is the test for reasonable diligence when it comes to the equitable estoppel?

Second, girlfriend asserts that boyfriend did not act with reasonable diligence in bringing suit once the basis for equitable estoppel endedthat is, once they broke up. "The rule of equitable estoppel includes . . . the requirement that the plaintiff exercise reasonable diligence." (Bernson v. Browning-Ferris Industries (1994) 7 Cal.4th 926, 936.) However, substantial evidence supports the trial court's finding that boyfriend was reasonably diligent: He sued girlfriend just over six months after they broke up; dismissed his lawsuit only after girlfriend declared bankruptcy (and sought to obtain relief from the bankruptcy court); and sued girlfriend again within two months of the dismissal of girlfriend's bankruptcy petition without a discharge.