Over 250k miles on my 2010 Toyota 4-Runner with 5-speed auto trans. I use the tranny/engine combination all the time coming down our steep grades here in the Rockies with never a problem. Except for no manual clutch, the technique is pretty much exactly the same as with a manual transmission.
The road grades on I-70 east and west of the Continental Divide are some of the steepest and longest in North America. That's crazy talk controlling descent speed with just brakes.
