CAL. FAM. CODE § 4336 : California Code - Section 4336

(a) Except on written agreement of the parties to the contrary or a court order terminating spousal support, the court retains jurisdiction indefinitely in a proceeding for dissolution of marriage or for legal separation of the parties where the marriage is of long duration.

(b) For the purpose of retaining jurisdiction, there is a presumption affecting the burden of producing evidence that a marriage of 10 years or more, from the date of marriage to the date of separation, is a marriage of long duration. However, the court may consider periods of separation during the marriage in determining whether the marriage is in fact of long duration. Nothing in this subdivision precludes a court from determining that a marriage of less than 10 years is a marriage of long duration.

(c) Nothing in this section limits the court's discretion to terminate spousal support in later proceedings on a showing of changed circumstances.

(d) This section applies to the following:

(1) A proceeding filed on or after January 1, 1988.

(2) A proceeding pending on January 1, 1988, in which the court has not entered a permanent spousal support order or in which the court order is subject to modification.