We have created an a-WEAR-ness Gauge to gauge wear and estimate belt replacement.
All serpentine belts need to be closely inspected to identify any and all wear. These belts are asked to perform in some of the most hostile environments because of high heat, contaminates and debris. Regular inspection of all drive belts and accessories should be mandatory once the vehicle passes 75,000 miles. Vehicles today have more accessories being driven by a single belt then in years past. Remember, if wear is ignored and the belt breaks, the vehicle comes to a dead stop!
https://www.daycow.com/daycow.nsf/aWEARnessGauge!OpenForm