Originally Posted by crabman
It isn't just wear in the trans its the entire drive train that should be considered. There can be no question everything gets worked harder in higher S modes so the real question becomes does it make any significant difference to the lifespan of any of the effected parts? I don't have an answer but one thing that is telling to me is that they made S6 harder to access and that wasn't done without reason. If you start thinking about what that reason might be its hard not to put drive train issues or failure before the warranty expires at the top of the list.
Usually when that's the case BMW will document that warning. I remember reading something about excessive wear from using launch control too often in the manual, but don't remember seeing something similar for S6 mode.
I'm speculating that in the case of S6 the harder shifts can increase the risk of lost traction which cannot be compensated by DSC, and could reduce overall performance and stability. I'm guessing this is why they allow access to S6 only with DSC off.