Welcome to a wonderful new world. With sous vide overcooking is different to how things over cook in traditional cooking. The longer you cook with sous vide, the more tender things become as the collagen contained in the muscle is converted to gelatin. This process happens very slowly at low temperature, but increases in speed with higher temperatures.
When cooking something, the best option is really to observe it. Pull it out of the tub every now and then and give it a pinch test to check on progress. See if it's becoming tender as you would like.
The very best teacher with sous vide is experience. The only way to get that is experimentation. But do it safely.
One of the best things to do is read Baldwin's work. A Practical Guide to Sous Vide