haha, you are thinking about this deeper than I intended. I only mean that if I keep it clean and maintain the engine so I'm not burning oil... You can say you would coat/spray/clean the frame, whatever you wish.
Bottom line is, the body panels start to peel and separate, electronics get moisture damage, mechanical parts wear out. Obviously you can replace parts all day, as KARNUT stated, one can obtain a whole new frame. But I'm not a mechanic and I'm not paying to re-build a car when its value is less than $1000. Some day that repair costs you more than the vehicle is worth. Do you keep buying parts? for how long?
All I'm asking is, how long do you EXPECT a truck built in 2020 to last for the typical responsible owner? Try to hit the mid-point of the bell curve.