Has anyone ever purchased the "tire protection plan" from 4 Wheel Parts? How does it compare to the "certificates" from Discount Tire? Looking at getting a set of new tires, from my experience with tire failure, Discount has been great in honoring their policy even in off-road abuse. The 4 Wheel Parts plan is ~40% cheaper, but is it as hassle-free as Discount or should I steer clear?