I don't get anywhere near 26,000k out of a rear, 13,000k would be pushing it too, but then again, I don't wear them down as far as you. less tread = more chance of a puncture.
Avon lasts me aaprox 26000km with some reserve. After switch to Metzeler I was satisfied with grip, but now I am disappointed from mileage. Rear tire literally sublimed in few days. Front looks relatively ok, raer has gone after 13000km. See photo. I bought next Metzeler, because was delivered on next day, but I hope to buy Avon again!