A California preliminary notice has, what we refer to as, sliding protection. Notice provided past the initial 20-day deadline will still be effective to secure lien/bond rights, but the value of labor and materials protected will be limited. Under Cal. Civ. Code §8204(a):
A preliminary notice shall be given no later than 20 days after the claimant has first furnished work on the work of improvement. if work has been provided by a claimant who did not give preliminary notice, that claimant shall not be precluded from giving a preliminary notice at any time thereafter. The claimant shall, however, be entitled to record a lien, give a stop payment notice and assert a claim against a payment bond only for work performed within 20 days prior to service of the preliminary notice, and at any time thereafter.
To sum this up, a late preliminary notice will secure lien rights (stop notice & bond rights as well) but only for the value of labor and/or materials provided in the 20 days prior to service of the notice and everything thereafter.
For more on this, see: The Ultimate Guide to California's 20-Day Preliminary Notice