You use it as a hobby machine, ie your livelihood doesn't depend on it working, you're not using it to farm. That's called hobby use. Same as I use my most of my equipment.
My current tractors stand just as much chance of making it 80+ years as anything from 1940 does. Wait, the numbers are grossly in my favor. 5 models of tractors, sharing 3 engines, and 4 transmissions. Hundreds of thousands of tractors sold in the 25 year production run, even the newer machines share 70%+ parts. Oh, whait the engines used are the D05 series, prolific in industrial use, million more made and sold to this very day.
In 1979 kubota celebrated selling 700,000 tractors and has sold over 1 million tractors in the usa alone to this date. Compact and sub compact tractors make up the majority of their sales. (FYI, nearly all the tractors kubota make are made nere in America too.)
The 9n in all its variants, didn't total 100,000 units built and sold.
so to put it simply, yes my crap will still be around, your old junk will run out of parts and fade to memory just like all antique stuff does.