This article on serpentine belts says:
"Vehicle manufacturers recommend inspection and replacement of the serpentine belt between 60k and 90k miles. Advances in material technology allow some belts to last more than 100k miles."
What were the advances in material technology?
As always on Stack Exchange, I did my own research before coming here, and I did find that neoprene belts were replaced with EPDM belts in the early 2000s. Perhaps the "advance in technology" was simply switching to EPDM rubber, but when I looked into when this "technological advance" took place, I see that EPDM was introduced in 1962 and became popular in the 1970s: So if EPDM is the aforementioned "advance" in technology, I wonder why it took until the early 2000s for it to be used for serpentine belts, was there a further advance in technology needed (?) or was it just that it was too expensive, or not enough in demand, or simply no one yet thought of using it for this purpose? I can imagine that if cars back then weren't lasting beyond 60-90k miles anyway, there would be less reason to switch to a material that lasts longer, and maybe that is indeed the reason, but most cars in the 1990s did last beyond 60-90k miles (albeit perhaps with lower resale value as a percentage of the original cost).