Which engine do you have? On the 4.8i at least the CCV is cheap and easy to replace. Their are two valves and each cost about $20 a piece and take about 20 minus to replace.

The D's never seem to die.

The inline sixes (I own a 335d/4.8i X5) I think, but I don't own one; have the CCV integrated into the valve cover. So they maybe harder to replace.

Yes, part of the CCV system on the 4.8i is integrated into the valve cover as well.