If you keep your processing constant then you run the risk of having negatives that have too great a contrast. That is the consequence of constant processing. One of the real things that happen with most films is that they will build contrast as the exposure gets longer. That is all he is mark is trying to control. I don't think you can say that something will go wrong in camera if the film builds too much contrast. That is the nature of most films. And when I say experiment I mean you need to know a base time for normal development and THEN deviate from that.