I've been getting conflicting opinions - maybe you guys with more experience on these eyewear will be able to clarify something for me. Is the hydrophobic coating on the Oakley lenses (Radars, in my case) permanent or not? Do you need the hydrophobic kit to "refresh" the layers every now and again, in other words.

And if it's not permanent - how long does it last before it needs refreshing? What causes it to shorten it's lifespan?