I rode high many times over more than a decade years ago and all through my racing days. Never before races but often on training rides. I noticed early on when I started racing that my reactions slowed as I went deeper into my reserves in races. And that this reaction slowing was very much like the slowing I experienced riding high. I started observing my reactions both racing and training high and believe to this day that riding high did a very good job of preparing me for the very hard long races to be a steady, solid rider that didn't cause problems and that other trusted. (And this with little group riding. The local group rides were in general, shorter and faster than I wanted to focus on plus they didn't work with my schedule. Also, quite a few of those riders rode high and shared stuff that I would have had trouble passing up. Safety-wise, riding with them would be like me racing high.)