Everybody seems to have missed bikenut's point and question. He's over tightening his cables and wants to know how to avoid this. Tight enough to hold isn't really a simple guideline, how do you know if it's going to hold. Do you tighten it, then race down your steepest hill at top speed and slam on the brakes and see if the cable slips out?
I'm facing a lot of broken cables and am wondering why myself. Overtightening may be a reason, but I'll explore that in another thread. There may be other issues. Here, I'm just wonder, like bikenut, what is tight enough - to make sure that when I have to brake hard the cable will hold?