The stock 19 staggered actually are a terrible size suggestion for rolling revs per mile. I think I read somewhere that on AWD vehicles the wheels need to be within a 3% difference as to preserve the Xfer case (transfer case). When running 18s this is not a problem because inherently the rims are the exact same size in all dimensions, therefore, the xfer case isn't constantly differentiating front/rear.

In this example of the 19s, we see that the rear wheel is actually smaller in circumference, thus, more revs/mile is needed. This would put stress on the xfercase as it would have to constantly differential the front and rear drive shafts. The clutches setup in the xfer case are setup to have some slip when the actuator is fully unloaded. This probably might not be a problem if the OPERATOR/OWNER of the vehicle follows the strict maintenance schedule of changing out the xfer case fluid every 30k miles--but if not, then the clutches in the xfer case end up wearing out until nearly full actuation does nothing to transfer power to either front/rear axle.

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2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6