In CA, must an attorney bill periodically (monthly, say) by law or regulations?

A Dec 07 retainer agreement that included a $10,000 prepaid retainer fee stipulated periodic billing no more frequently than monthly. The terms of the agreement required replacement with another agreement once the retainer amount was reached. The attorney never offered another agreement once the retainer was passed, and failed to bill the Non-Profit for 17 months in spite of numerous requests to do so. After a successful result, and into the next year (when donations for causes became far more difficult to raise) the attorney presented a bill for $215,000. The delay from Spring 2008 to May 2009 in presenting the bill has made the continuing viability of the non profit in doubt and seriously hampered fund raising activities so far after the fact.
What legal rights does the Non-Profit have