I had a Valeo 140A alternator and it failed completely at 91k miles but 13 years of age - Left me stranded and needed a power pack to limp it to the dealership over the summer - not sure if it was the bearing that failed or the voltage regulator but it was dead as a doornail -

So in my opinion not as much about mileage but age -

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards