In my younger days, we had a new walkway bridge open up near our building at work. The opening was announced months in advance and the bridge opened on the exac

In my younger days, we had a new walkway bridge open up near our building at work. The opening was announced months in advance and the bridge opened on the exact day they had said it would. I remarked to my wiser boss (also a software dev), how come they can predict their bridge completion so accurately while we continually run over and have to cut stuff to make our dates? Ah, he said, we never build the same bridge twice.