Maybe it's like when a relationship ends and someone resorts to "it's not you, it's me". Well, I don't know if it is because I am doing something wrong and don't know it, or if the design of Presta is so,inherently weak, but I seem to blow through inner tubes on a disturbingly regular basis. Often enough that I an now buying them 4 at a time and always carry one on board when I ride. I manage to break off the little central whatever it is called, and that's that. Sooner or later they are toast.