Temporary vs long-term
Temporary spousal support is computed by formula in most California counties (Santa Clara, Alameda, etc.) and is intended to maintain the status quo while the case is pending. Long-term spousal support — set in the judgment or after trial — is decided under the Family Code section 4320 factors, which the court weighs case-by-case.
The Section 4320 factors
The 4320 factors include the marital standard of living, each spouse's earning capacity, the duration of the marriage, contributions to the other spouse's career, age and health, history of domestic violence, and others. There is no formula — the court weighs the factors and makes findings.
Duration considerations
For marriages under ten years, the rule of thumb is that spousal support runs for half the length of the marriage. For marriages of ten or more years (a "long-term marriage"), the court does not set a presumed end date — the supported spouse has an obligation to become self-supporting within a reasonable period, but the order may continue indefinitely subject to modification.
Modification and termination
Spousal support is modifiable absent a non-modification clause. It terminates on the death of either spouse, the remarriage of the supported spouse, or further order of the court.