This is quite different than altitude sickness. Taking a break or not doesn't really matter, a body either handles it or it doesn't. At some point going up is not a good idea at any pace.
With all the peaks you've climbed, I wonder if you ever had any amount of AMS?
It's well established that we can climb higher than we can sleep. When you’re not acclimatized, and you stop to catch your breath or (even worse) try to sleep, your breathing may slow down to the point that you’re not getting enough oxygen. That’s when you may get sick. If you hike at a moderate speed, you will breathe correctly, even if you’re not acclimatized yet. Keeping a steady pace is not only the most efficient way to climb, I believe that it actually helps avoid AMS.
When I did my “Whitney Double” in 2010, I stopped as often as needed for water, food, clothing, potty breaks, etc., but I only took two “sit on my ass and rest” breaks the entire day: one at Whitney Portal between trips and one at Trail Crest on the way down the second time.
I had mild Cheyne Stokes breathing above 14,700’ on Denali. I took 125mg Diamox and I was fine within a few minutes. I actually felt pretty good on the summit at 20,320’. I have never had any issues in the lower 48 states. When I climb 14ers, I usually don’t even notice the altitude, and I never get sick. I’m very lucky!
