It is to the auto makers advantage to make vehicles that rust out fast. There is zero incentive to do better. On one hand the faster vehicles go bad the more new ones will be sold, on the other hand if they give up too soon customers will be unhappy and buy something different. Therefore they are designed to last only so long, but not too long. Since rust usually takes over after the vehicle is paid for and warranty is off, there's reverse financial incentive to make them better. I heard of one man in the industry who carefully designed a vehicle that would be easy to repair, and of metals and materials that would last forever, and tried to get auto makers interested. No takers. He was finally told his car was too good. Once the market is saturated with such a vehicle sales would drop off, just selling to newcomers and wreck replacement, because they last so long. Why is a consumer grade auto high mileage at 200,000? There's a reason semi trucks run to a million miles or better on a regular basis before an engine rebuild or major work. They are intended to. If they didn't we'd have a lot of unhappy truckers. Then I heard of one man who ran a semi to 750,000 miles with hydrogen feed to the diesel. Had an engine teardown inspection done by a mechanic, everything looked almost new, so he put it back together and kept going. Hydrogen (or hydroxy as it's produced onboard from water and not separated from oxygen) causes the diesel to burn more efficiently eliminating carbon deposits that wear things out. Boosting MPG by 20-50% while it's at it.
Those trucks can run as much as 1200 miles per day, (2 drivers at 11 hours each) and keep it up 6 days a week for years. (7 days would require extra drivers because of the restart rule requiring an extra time break once a week) We bought an 03 mack in 2014 that had 800,000 miles on it, started driving it and repairing stuff as needed. It's well over a million now, but we did finally have to change engines last year with somewhere around a million on it. I drove it with a friend 3 months and then my brother and cousin took it awhile, then we hired a driver. Now the hired driver is on a leased truck and ours is making a run to the west coast with our friend and his father. (He's serving as dispatch and general manager) Looks like we could be into 5 trucks before too long. My brother just bought an old 70's ford dump truck with 534 CI gas engine in need of rebuild, hoping to get it going and restore for a medium duty car hauler. Really cheap truck, guess he got it for a few hundred dollars, but would take a lot of work. Wouldn't be my choice to start on, but that's OK. At least it would slip by several of the trucking regulations. Like electronic logging and CA smog regs. Can put hydroxy on gas too, boost mpg and reduce engine wear, but have to figure out how to reduce fuel delivery, sometimes the automatic mixture controls don't adjust to the more efficient burn on their own.
I'm in TN, they use a little salt but not much snow to use it all the time, and local vehicles are pretty good about lasting. But get one from up north and it's usually in bad shape. I traded for a 93 jeep cherokee from Ohio once, later ended up selling it to a scrap yard even though it still ran. It was too rusty underneath to be safe on the road, axle stabilizer arms could fall apart. The two Isuzu pickups I have about the same age are from south and north, the 4x4 I'm fixing has a rotten out frame, the 2 wd from local is in great shape. So I plan on combining them somehow. Front part of frame on 4x4 looks OK, it had enough oil leaks around the engine to keep it from rusting out, from under the cab on back it would be on the ground if someone hadn't reinforced it with angle iron. So I'm thinking of possibly cutting the frame in half on both and welding the good one from the 2 wd truck on the 4x4 front end, might be easier than to attempt a complete transfer of all 4x4 parts. Would like to make it my regular transportation.