Mileage is actually impossible to tell because everybody has such different riding styles. Also we have to realize that softer tire compound, better corner grip, stopping, and offroad traction always equates into shorter life.
Let's use the TK80 for example. I have heard guys that get over 6,000 miles on a set and others that wear them down to the bars at just over 2,000 miles.
For me I have always been happy with a tire that will last between oil changes. 3000-4000 miles is an outstanding life for a quality tire that performs well. On my old Ninja 650R I was running Michelin Pilots. They would last just over 10,000 miles but performed like crap after around 5,000. The cornering and braking deteriorated after that.
My Kenda Big Blocks are done at about 2,500 miles.