I can't really help - I've had two E93's and my current E92 and didn't get 20,000 miles on any of them (my E92 M3DCT ZCP just broke 12K), but Phrozen06 got 222,000 miles on his M3 before it was totaled.
http://www.m3post.com/forums/showthread.php?t=1414444
What do you fly?