I have, but how you brake is going to be the determining factor here, not the pads.
The fact that you say "drag brake" gives the impression that you brake for long periods of time, which is going to go through pads much faster than periodic hard applications of brakes using both brakes, with the majority of pressure on the front.

Ive used salmon pads for many years, but while I havent used them a ton in mountains, I tend not to brake much, and when I do, its a short, hard application using mostly the front, and I as a rule never drag my brakes, so over the decades, my brake pads last a long time.

I know I'm not giving you an exact answer, but I can say that when I started using them, I thought they might wear quickly, but in the end, they have not, and I am very happy with the increased stopping power they give me compared to the stock pads that one bike came with. My other bike with them doesnt see much brake use, its my winter rider, and I am hardly ever going more than 35kph, and I mostly am going slow, so have minimal braking, so the salmons on that bike are ancient.