I changed mine out to EBC HH pads at @ 25K miles. They still had a fair amount of miles left on them, especially the non linked caliper's pads, but I tend to replace items like that too early.
I just had mine replaced my front brakes at 16800. I did do a lot of mountain riding, but its been years since I have had brake pads with so little life.
Too many variables for this to determine anything, I changed mine at 30,000 miles but they still had life yet. I was already doing a brake service so I changed the pads at the same time.
I changed my rear pads at 12,500 miles, fronts still have plenty of life in them. Did some mountain riding and rode the rear brakes a lot.
I am a firm believer in stopping with the brakes and not downshifting that much. Pads are way cheaper to replace then a clutch pack is!