Having recently gone a couple rounds with the CCV system on an M54 myself I'll say this much. The cold can play a significant role in how the CCV behaves from one day to the next.

As soon as it started getting down to freezing temps the build up of the mayo on the bottom of the oil cap was thick and this was on a CCV system I replaced less than 5000km ago.

I'm sure you are aware, but just in case...a quick test is to take the oil cap off when the engine is running and if you feel a vacuum then you can pretty much bet money your CCV system is shot.