[MysticBlue]

There shouldn't be any physical difference between being in N or D while stopped, as far as the clutches are concerned. In neutral, if you give it throttle, the computer will not engage either clutch. If in D, if you give it throttle, the computer will engage one of the clutches. As far as wear on the clutch, unlike a dry clutch, the DCT clutch is engaged hydraulically and is disengaged at rest. In other words, hydraulic pressure is what engages and keeps the clutch engaged. Lack of pressure allows the clutch to disengage, so there is no wear during disengagement. (By wear, I assume you were talking about the throw-out bearing on a conventional clutch). So, worrying about wearing out the the clutch bearing due to clutch disengagement is a moot point in the DCT. Which is a good thing, since there is ALWAYS at least one clutch in the DCT which is disengaged, and while stopped, both clutches are disengaged.
So if you were putting it in N every time you came to a red light, thinking you were saving wear on the clutch, you're not.