If your employer has more than fifty employees and you have worked there for at least a year, your employer must hold your job open for at least twelve weeks pursuant to the Family and Medical Leave Act (and California's Family Rights Act). Beyond that, your employer is under a continuing duty to "reasonably accommodate" your disability pursuant to the Americans with Disabilities Act (and California's Fair Employment and Housing Act).
Whether keeping your job open constitutes a "reasonable accommodation" is subject to many factors, including the nature of the work you perform, the size of the employer, its business needs, etc.
In light of this, there is no hard-line rule obligating your employer to keep your position open for the duration of your disability, although doing so may constitute a reasonable accommodation.
Mr. Sheppard has it right. Under other areas of the law there may be some requirements but not under workers' comp. You could be terminated in a day or a year depending on the circumstances. They key is that they cannot treat you any different from any other employee who is off work for medical reasons.