There is no problem as long as mail can be delivered to your address in China. I had a problem once, due to LH IT problems I could not enter my HKG office address properly. I did not receive any newsleters and promos during this time, my MM account worked normally though.

The only thing that will change that if you are logged into your profile and want to do a booking, you will be redirected to the LH CN site. If you need to book from LH.de, you cannot be logged in. Then you have to add your MM number later to the booking.