As briefly mentioned above, the E-Diff works by utilising itself and DSC, by braking the inside wheel (rear obviously, being RWD!) under power-on cornering to prevent excessive, pointless and embarrassing inside wheel spin!
So, OP, it depends on your driving style! If you like to put your foot down through corners (and which BMW driver doesn't?!) then the E-Diff will do it's job to a greater extent, naturally leading to more wear.
Depending on to what extent, you may or may not see the DSC light flashing on the instrument panel.
DSC does, to a small extent, work in the background without notifying the driver.
Also, traction loss and DSC intervention will increase brake wear, again, depending to what extent and what conditions.
2006 BMW E60 520d SE 6MT
2009 BMW E90-LCI 330d SE 6MT
Current: 2012 F30 328i Luxury 8AT
2015 Audi A6 Avant Ultra, Black Edition (sorry!)