My TJs don't see winter duty here in Mass, but my old 3rd gen dodge ram does. I bought it when it was a few years old, and it's 18 now. Originally I used to run it through the undercarriage washes as often as possible after the roads were salted. A few years later a buddy of mine and I bought the fluid film guns and a 5 gallon pail of the stuff and started doing that to our vehicles. It's really been amazing. I have an 18 year old 3rd gen Ram in Massachusetts and the frame is perfect. I didn't start doing it in time to save the bed, but I replaced it with one from Texas and now it's floating in fluid film. I also bought some body plugs for the inside of the rocker panels. I fluid film inside them and then replace the plugs. I've also been known to take the door panels off on occasion and spray in there. I really coat the living hell outta the poor thing.
Boogieman makes a good point: it does wash off, but another poster had the right answer, you don't wash it after you fluid film it. Not until spring. It doesn't come off all that easy though, running it through puddles and such it holds on pretty well, but I try to avoid this as much as possible.
Now, it does have a bit of an aroma, but its not horrible, and it makes working underneath it very, very messy.
I have no idea what the dude from Minnesota is using, I've never tried it, but that LJ frame does look nice, and if he's been able to keep it that nice for that many years while seeing winter duty in Minnesota, that might be worth checking out as well.