My dealer just replaced the cylinder head on my 2006 Z4. Bought it CPO and noticed the noise when I first drove it off the lot and the salesperson suspected the noise was a low octane "ping", maybe the previous owner had not always used the proper fuel. Had the bleeding procedure done about 4 months ago before a 1000 mile highway road trip. Even after the trip and more than a few high speed stretches, ticking still would return and was getting louder, even though the bleeding procedure worked to quiet it initially. Ticking is gone, engine sounds great now. The dealer never said the noise was damaging, but I never believed it could not be harmful so I persisted.....it just didn't sound right. My first BMW was a 2004 330xi and I never heard anything remotely similar from that engine.
Love the Z, and cruising with a tick, tick, tick was downright embarassing.
