Independent bodies have been testing thin oils for decades and there’s no evidence of excessive wear compared to heavier oils. Chemical composition and age of the oil are the actual factors you need to worry about.
From a practical perspective 0W-20 has been common in cars for well over a decade and 0W-16 was not too far behind. Given that owners are notoriously poor with maintenance, if these oils were causing excessive wear and actual damage we would have heard about it a long time ago. There are 0W-16 Civics and Corollas out there with hundreds of thousands of miles on them.
Of course there are specialized use cases where it might make sense to swap out your oil for something thicker. Track use is one application that comes to mind. However, they’re doing it for thermal management during extended WOT conditions and not due to viscosity.
Of course, the cargo cult idiots always believe that it’s a 1-to-1 analog; if something works on a track car then doing the same on a road car means it will run forever. These people ignore the fact that race cars require constant maintenance and frequent oil changes. Racing is about stable performance over the course of an event, not long term reliability. They’re not worried about potential issues from running thicker oils because they have a specific need that justifies the compromise.
Americans average over 14.2k miles a year which is higher than I expected but I assume that’s due to long commutes.
There’s no such thing as too many miles. It’s all about driving conditions. City driving, with its constant start-stop cycles is far harder on a car than someone doing long cross country trips on the highway. Of course, maintenance and overall age are also important considerations. Some components degrade even if the car is sitting in a garage.