Had to replace mine early due to a nail, an since I had a track weekend coming up I couldn't safely use a patch (wanted to get PSSes anyway), but based on tread depth I probably would have reached 2/32" replacement time at around 12K on the rears and 15K on the fronts. Those were PS2s, which have a 220 treadwear rating; the PSSes have a 300 rating. My driving is roughly 50/50 city driving and harder back road + track driving, almost no freeway driving. I don't kick the back out around turns or anything like that.
I admit I was expecting a bit more life than that but it's still worth it IMHO. The tires are great, the PSSes are a lot cheaper, and you gotta pay to play I guess!
'16 Cayman GT4 (delivery pics
Gone but not forgotten:
'11.75 M3 E92 Le Mans | Black Nov w/ Alum | 6MT (owned 5/2011 - 11/2015)