If you don't track and drive mildly...I would think you should get over 25K+ miles on the fronts & a bit less on the rears....
However if you track....it really collapses quickly...for example my 928 (front engine rear drive, same weight as M3, with 330hp) conti sport contact II's that came stock on a 2006 911 have about 7K miles on them and are around 30% rear and about 65% front...but thats after 4 track days and lots of aggressive street driving
2008 E92 M3, MR, DCT, extended BB leather, loaded!
1988 Porsche 928S4, Guards red/Champagne leather
1989 Porsche 928S4 track beast!!!