The risk isn't losing braking capability; the risk is blowing a tire at speed.

You'll know when the brakes are getting too hot, well before they become inoperable. You can both here and smell it, as the brakes start to off gas.

So if they do overheat, you just have to stop and let them cool. You'd have to ignore a lot of warning signs, and possibly blow a tire off, before you lost the ability to brake.