The first set of rear pads on my 2014 GS LC were apparently 50% worn at the 6k service, but were virtually down to the metal 2k miles later in northern Italy after a few days in the Alps.
The replacement OE pads fitted by an Italian BMW dealer were supposedly 60% worn at the 12k service, but had only just gone below minimum thickness when I changed them at around 16k.
The replacement EBC pads were then apparently 60% worn at the 18k service, but were OK until about 23k miles.
So 7-8k miles seems to be the norm on my bike. I rarely use the rear brake, but nearly all my mileage is two-up on the twisty roads of the Yorkshire Dales, Lakes and North Pennines