You may remain president as long as you like if there are no bylaws. However, I would reccomend that you put bylaws on your agenda as soon as possible. No matter how well things are going they are an important backup.
We do not have any by-laws in our group. I have been president for 2 years now and really enjoy it. I get along well with the principal and the teachers. My committee and I have accomplished alot the last 2 years. Is there a ruling on how long one can be the President of their PTO?