I have a 65 gallon tank, that's been set up since 5/01/06 (13 1/2 weeks). The tank is healthy AFAIK, 0 nitrite, 0 ammonia, 7.8 pH, 80 nitrate (should be zero after a PWC).
I am successfully keeping healthy, happy fish in it, and the only death, to date, was a Bristlenose Pleco, whom I purchased...