http://www.homepokertourney.com/blinds_samples.htm
Well i know for 10 players, the tourney should end when the blinds = the buyin (or 1/10th of the total chips in play). Id assume that the tourney would have to end by the time the blinds reach 1/10th of the total chips in play (or 30,000 in your case). however, it would probably end faster than that