Your technique is correct but your understanding of the physics is wrong. You're getting confused by the braking at corners. You're not braking at the corners because you're concerned about heat. You're braking at the corners because if you don't you'll crash. Later when you're sitting in your armchair you mull it over and pretend you did it for heat control.
No, my understanding of physics isn’t “wrong”. I know that I’m braking at corners to maintain control. I’m
not braking in the straights to avoid heat build up…at least not braking constantly in the straight parts to avoid heat build up. I pulse brake in the straights if the speed is getting too high for comfort. My tolerance for speed is probably a bit higher than most people, however.
But have you ever ridden a descent with no corners at all? I have. Here it is on the map. And here is a photo of the top with an elevation sign. It's a desert pass over the Altyn-Tagh. The word "pass" is being used loosely here. It's actually one way slope up onto the Tibetan Plateau. 8000ft elevation change top to bottom. Most of it is dead straight on alluvial fans. Part of it is through some rocky hills but the road is engineered for high speed traffic so the curves are large radius and don't require cornering. You can get a tuck on this descent, never touch your brakes, and bomb 50+ mph the entire way down. But you won't do that because you don't have a death wish right? What if you hit something on the road and blow a tire at that speed? You're dead. But what braking technique do you use when there are no corners to force you to brake? Do you pulse, alternate, or light drag? The answer is it doesn't matter.
Yes, I’ve done lots of relatively straight long descents. Probably not 8000 ft ones but lots of others. You don’t say how long this 8000 foot descent is but isn’t going to happen in 3 miles. Very long descents don’t really require that much in terms of braking nor would I expect the wheels to heat much in those conditions. Yes, I agree that your brakes are going to have lots of opportunity to cool on that descent. But you also aren’t likely to drag your brakes over a very long descent like that. If you did, the descent would take forever and your brakes and wheels
would get very hot. Dragging brakes on a very long descent is not a good idea.
Heat management is like dieting. If you eat 15 cheese burgers a day you're going to get obese. It doesn't matter what interval you stuff your face at. All that matters is total energy in energy out. If you dump more energy into your rims per minute than they can lose, you will overheat eventually. It doesn't matter what braking pattern you use. If you maintain a high average speed you'll lose more energy to air resistance and have to dump less energy into your rims. That's the only thing that matters.
The hamburgers is the wrong analogy.
However you are so close to understanding. I agree that if you dump more energy into your rims per minute than they can lose, they will overheat. But if you aren’t dumping friction into the rims…i.e. pulse or “on/off” braking…you aren’t dumping any energy into the rims when the brakes are off. If you are constantly braking whether lightly or strongly, you are constantly dumping energy into the wheels. The wheels can’t shed all of that energy and they overheat, thus the need to stop and “let them cool down”. That cool down period is a time of no energy being put into the system which allows the heat to radiate away…just without the air flow you’d get if you were riding without the brakes on.
Here's another thought experiment: is it better to alternate drag front and rear, or drag both continuously at half the hand pressure? The answer is, again, it doesn't matter. You're dumping the exact same amount of energy per minute into your two rims. When you get to the bottom of the descent and measure your rims, you'll find that the temperature is identical between the two techniques.
You are missing the third scenario…not dragging the brakes at all. In the scenario where you are pulse braking…i.e. brake hard, then no braking, then brake hard, ad infinitum…you are putting the same energy into the system but there are periods of high energy input and periods of no energy input or even negative energy input as the air pulls the heat away. At the end of the descent, pulse braking rims will be cooler than if you drag the brakes all the time.
For the record I alternate drag between front and rear. It's not for heat management. It's for my hand muscles. I never do the fast-slow-fast-slow boink boink Slinky style. Riding like that is stupid and annoying, for both myself and anyone else riding with me. I sit up straight to catch the air and try to not use my brakes at all. If I have to use my brakes I heat manage with my ears. When your brakes start to overheat you'll hear the sound change. At that point I pull over and take a photo break. When you are on a big mountain descent the scenery is usually pretty good.
Who is taking about your “Slinky style” of braking? I don’t do that kind of braking, nor would I suggest it. When I brake hard, it isn’t to a stop or even to a super slow speed just to go around a corner. I know how to corner fast. In my experience, brake draggers are usually the ones who do the “slow-slower-slow-slower Slinky style” braking on steep, curvy downhills.
Frankly, I don’t pay too much attention to my brakes while riding. I don’t hear a sound change because I never get my brakes and rims hot enough to make that sound. I pull over to take pictures because I want to, not because I need to.