That's all well and good, but the fact remains that there are plenty of other similar vintage and older vehicles on the road that travel through the same salty slop that our vehicles do. Somehow those vehicles haven't all rotted to the core. Every vehicle is different and even essentially untreated steel will last an eternity in the desert. These trucks were made with the full intention of being used in wintry climates yet in my opinion they are sadly unprepared for "normal" conditions of use. Your car shouldn't have to be washed after every use. That is ridiculous to expect such a thing. No personal offense intended towards anyone, I am just venting a bit. :dammit:
Every vehicle I've ever owned, it stated right in the owner's manual that for the longest service life, the vehicle needs to be maintained. That not only includes preventive maintenance of the mechanical parts, but maintaining the body and frame by washing off corrosion inducing chemicals as necessary.
The manufacturers know that even with the best rustproofing methods available, if a vehicle is driven in highly corrosive conditions, and little to no effort is made by the owner to clean the vehicle as needed, it will eventually rust away. That's why they are only warranted for rust for a limited amount of time. They have determined that even with complete neglect, the vehicle can usually make it through the rust warranty period.
Look, I used to work on consumer cars for a living. I saw all makes and models rusted out due to neglect. I still have friends in the auto repair business that tell me the same thing today.
Some people do a better job than others of maintaining their vehicles. Some people just put gas in them and drive. Maybe they get the oil changed once in awhile. But wash the undercarriage in the middle of Winter?!?!, that would be cold and inconvenient..
Of course when the neglectful Owners vehicles do rust out, they blame the manufacturer. Instead of their own neglect.
Toyota's can last a long time, if they are maintained. If not, they will eventually reach the point of being beyond reasonable repair. As with any make or model.
The newest 3rd gen is now 13 years old. 13 years is well beyond Toyota's rust warranty period.
I'm not trying to piss in your Cheerios, I'm just explaining the reality of the situation. I'm guessing that you are probably not the first owner of your 4Runner, and that it was neglected by the previous Owner(s).
My advice if you don't want to have the rust fixed, is to buy the new 4Runner, and maintain it better than your current one was.
Good luck.