I purchased the 06 in Dec of 09 as a CPO, I doubt that the dealership put these expensive Michelins on, so they were probably installed by the previous owner (car had 30,000 miles at the time I bought it)
But 4 Years old and cracking?
The car is used every day and kept outside, mostly local driving with an occasional trip to Orlando.
I replaced the tires with YOKO AVID's because they are relatively inexpensive and TIRE RACK gave them a good (quiet) rating, $100 each less than the Michelins...
And I'm still trying to sell it or trade it up for an 09....then again this car has been so good that keeping it is another option, (more money for my Z3 restoration)

__________________
BMWCCA # 12660
14 GLK 350 M/B (hatefull POS gone)
05 CLK 500 AMG Cabrio
07 530xiT
09 Boxster