I commented yesterday on the life span of a Ford Jubilee tractor, or for that matter, any of the old tractors.
With proper maintenance and occasional work as needed, these pieces of equipment will run a long time.
That's one of the things I like about heavy trucks.
You can take almost any of the common older trucks and update it with safer brakes and plumbing, freshen up the diesel and do normal maintenance work, and it will serve you for as long as you want it to. Then you pass it on to the next owner, and it keeps on working. It is pretty unusual to find a truck that is so far gone that it cannot be saved, unless it has been parted out or wrecked.
New trucks might be faster (maybe), or might be more fuel efficient (unless the electronics are acting up), and they could be more comfortable - but - they are a lot more expensive, and unless you are working it hard every day, the new truck probably can't match the financial efficiency of the old one.
Recycling in the most pure form!