I believe it's all based on riding style and where you live. Me, being here in central Florida don't get to ride twisties that often and I'm not an aggressive throttle man. I do alot of straight line I-95 commuting, with the occasional speed run up to 185 indicated when I'm froggy. I do have sort of a flat center tread area, but still less than 1/8" chicken strip. I try to use all the tire when I can.
I just turned 6000 on my original OEM's, and I believe I just hit the wear indicator on the rear. The front still looks really good. New rear just arrived today, it will be installed soon. After that one is done, then I'll replace as a set.
Be safe,
Jay