I've seen estimates as low as 4 years/60,000 miles (from places like NAPA, who obviously want people to replace their belts and hoses all of the time) to 7 years (from an anonymous Gates engineer), to 10 years or longer.
I find 4 years to be outrageously low and there's no way people are actually replacing their belts and hoses after 4 years of service.
I previously had a Honda Accord with 271k miles which was 28 years old at the time with all original belts and hoses on it. (I suspect these were on borrowed time, but still - they hadn't blown up yet). My current vehicle (GMC Envoy) is 15 years old with almost 130,000 miles with the original belts and hoses.
What is the actual useful service life of modern EDPM radiator hoses and serpentine belts?
For the purposes of this question, I am not asking about the cheap (non-EDPM) aftermarket parts which obviously have an abbreviated lifespan.