I've pondered this question a lot. My current thought is, this is a piece of metal, no matter what you do to it, it will slowly decay and rust until it is unusable. But perhaps I am wrong. For those of you who have undercoated or POR-15'ed their frames, how well have they held up? The older the better. Every time I thought about undercoating my ex-Jeep, I always saw it as pointless, since there's no way you can get to the inside of the frame, and then it'll just rust from the inside out, I mean, aren't you just delaying the inevitable?