At 11,400 miles I swapped my RE070's for a set of KDWS' (which are going to have to pass for winter tires this year). I found that over this span I'd used 1.5/32"s (9.5/32"s new vs 8/32"s now). All things being equal (they never are, are they?), and figuring that I've used one fifth of the usable tread life of 7.5/32"s, my RE070's have 45,600 miles left in them and should have a total usable life of 57,000 miles.
I'd characterize my driving style as hard but I don't abuse anything either. Of course, YMMV.
BTW, the tires are for sale but I'd like to limit them to New England delivery only. Alan