the "brittle & dry" of most plastics is not due to the material oxidizing. It is more a break down of bonds within the molecular structure of the material, usually due to UV radiation. Additives to the plastic can be added to avoid this. The other part is localized friction, when you neglect to wax. This is more of a "base burn", again, the structure of the p-tex changes at the surface. Basically the pores becomes closed up. Waxing alone will not rectify this. You have to expose the structure again. You can try brushing from tail to tip with a steel or brash brush to open up the base again, then wax. If that does not work, then you'll have to get the base ground.