Pulled the stock SR-A's at 15,000km on the FX4 - they were 30% done. Have 26,000KM on the truck now with Duratracs.
Had Duratrac's on the XLT from day one; the first set lasted me 45,000km which was what I expected.
Good tires, not long lasting though. I budget for two sets of tires every year based on my driving.
I could have gone to about 50K on the SR-A's on the FX4 but they were already sketchy in the snow when brand new.