2 track weekends (4 track days, 4 sessions/day, 16 twentyish minute sessions total) on one set of pads is pretty good imho
And even at that you've got to keep in mind your getting more heat transfer through the pads and into the fluid/caliper towards the end due to the decreasing thickness.
What kind of wear are others getting?
Edit: This is assuming 1/4 or more pad left at the end. Reasoning stated above. Also the second half of the pads wear slightly more quickly due to the amount of heat cycles the deeper pad material has already undergone.