It is a one-time application with lifetime warranty. The guys says that undercoating will also help keep the road noise to a minimum
It's actually detrimental to the vehicle. We apply the same crap to new cars at our stores, but for much more money. If I were looking for a hobby car, and MX5s would be considered to be in that group, and the owner said he had applied that sticky crap to the bottom of the car I won't even consider it.
You don't understand, as with others here, the concept of Krown. It's of a different substance, but it's like spraying the entire vehicle inside and out with WD40. It hit's everything but brakes and belts. Great for wiring, bolts, everything metal. It eventually disappears and needs to be redone.
It's for long term ownership.
If you can't find Krown or something like it, AFT would be better than nothing.