Try to stick a phone down there and get a picture/video of the balancer hub to see if you can see any cracking in the rubber. Good time to replace if you notice anything.
People are installing a clutched alternator pulley in place of our solid one to try to get more life out of the stock balancer (nothing proven yet). 335d/x5d take different size spacers on the pulley for proper fitment.
Here is a link to the clutched pulley w/ spacer kit.
http://www.fixmyvw.com/decoupler-pul...-35d-and-335d/
Will be installing a fluidampr & clutched alternator pulley this week sometime. I like the counterbalance concept of the fluidampr, hopefully be silky smooth!