I posted a reply here earlier, but then went in and deleted it after reading comments from opposing views that made sense. Basically, Gerald reflected my resulting point of view, to each his own, though I retained my inclination that the EB and brake lamps should coincide. I could see both sides of the issue. After more thought about the time I experienced severe brake fade in a small pickup on a 10+ mile downgrade, I realized the result is my tendency to keep my coach at or below posted truck speed when on steep or curvy inclines. I certainly don't do 60+ mph on them.
The Speedy Gonzales approaching behind me deserves to know that I'm not at, and possibly nowhere near, his speed. As Marty indicated, if you are doing it right, the EB should hold the coach at what you personally deem a safe speed for the nature of the road, without your touching, and unneccesarily wearing, the fade-susceptible service brake. But counter to Marty's conclusion, given the above circumstance, that speed may be well below Speedy's, and illuminated brake lights add a measure of warning that I don't think should be ignored. If circumstances are severe enough, I reckon flashers are in order, but I really think they're more useful to fully-loaded commercial semis.
I believe my lamps come on when the EB engages, and I guess my philosophy is if it ain't broke, don't fix it.
Just my 2 cents-
Joel