I hear great things about noxudal and I have no reason to doubt them. Even so, I'd still like to see a noxudal application after one year in areas that get moderate to heavy road-wash.
The reason I say this is even, run of the mill FF or WW stays put beautifully in areas that don't get road blasted. I can show you 1-2yr old areas of FF and WW on my Ram 1500 that look like I sprayed them yesterday (above heat shields, fender liners, inside of front bumper, above fuel tank). The floor sheet metal holds the product well also. It takes on a black, greasy consistency in those areas as dirt and grit into it.
On the other hand, I could apply FF, WW, etc with a mop (kidding) onto the frame and chassis components in direct contact with tire/road spray and it will be (visibly) gone in a month.
My take away with oil or wax type rust proofing is, if the vehicle lives in the rust belt, ANY of them are better than nothing. If you're conscientious about re-applying it at some reasonable interval, they'll all help and the chances of them working gets exponentially better.
Living so close to the Canadian border where Krown has prevailed forever, you should see some of the old iron there that looks new underneath due to yearly Krown re-sprays. I tried Krown in the Buffalo area once. To me it seemed like thinned vegetable oil and was visibly gone under my vehicle in no time. Would it have been better year after year? Maybe..