I feel the improvement in lubricating oils has helped also.
As a young boy in the early 50's a lot of cars/trucks were seen with a blue clouds coming from the exhaust if they were a bit older.
As oils improved, that disappeared, also ring design/materials have improved.
As a teenager I spent some time in a friends junk yard, not only getting parts but working on saturdays doing what ever was needed and a lot of cars were junked with less than 100,000 miles on them.
Today normally 200,000 or more is expected before a engine major is needed.
Improved oils, material design, and overdrive transmissions all contribute.
Also we run them a little hotter @ 195* rather than *160-180 as well as positive crankcase ventilation to reduce sludge/moisture buildup.
Just my take.
