Probates in California have built-in delays. First, the court has to hear the probate petition. How quickly it is heard depends on the court and the particular judge. It could be six weeks. It could be six months. It could be slightly shorter or a lot longer. Then, the court has to sign the papers giving the personal representative the power to administer the estate. That can take days or weeks.
Once the petitioner is appointed and the papers issued, creditors have to be given four more months to file claims. At the end of that four months, the Final Account, etc. can be filed. The Final Account also needs to be heard by the court, which means another delay like that for the original petition.
If the Final Account, etc. is approved, the order must be signed and the assets distributed. Once the distribution is completed, including recording all necessary documents, and when all receipts and releases have been signed, the personal representative can petition for discharge. Once the discharge is granted and the bond, if any, has been exonerated, the case can be closed.
There is no limit on how long it can take, though at some point the court will have to be informed as to why it is taking so long. Some have taken decades.
This describes a normal probate proceeding. Even where someone has died without taking the necessary steps to avoid probate, there may still be a way to bypass the court process altogether or an available proceeding that is less expensive and time-consuming than regular probate. I am familiar with these and may discuss some of them later.
The statements here are general and may not apply to specific situations. If you have a specific legal problem, contact an attorney.