Hi!
Check your state's Corporations Codes. There should be a section for Non-Profit Corporations. In California, this is what the code says:
5213(c) If the articles or bylaws provide for the election of any
officers by the members, the term of office of the elected officer
shall be one year unless the articles or bylaws provide for a
different term which shall not exceed three years.
This applies to officers of the board of directors. There were no term limits for the other members of the board of directors. The officers should include, President, VP, Secretary and Treasurer.
For PTO's who have incorporated in California, you can find the California Corporations Code at this website. Be sure to scroll down until you find the section for "Non profit Public Benefit Corporations."
I hope this helps!
(Here's the website):
California Corporations Code