Actually, the owner's manual on my 2009 FLHTC states the pad thickness should be more than 0.016 in. (0.4 mm).
At my 15k service, the dealer told me I needed new front pads. I checked them, and I still had about 1.5 mm. I orderered LRB pads. I now have about 19k miles and I still have more than a mm.
The LRB backing plate is 3.20 mm. The total thickness (pad & plate) is about 6.9 mm. So, if you go by the old "as thick as the backing plate" rule (which seems to be a great rule in the auto world) , you may be throwing out a lot of good pad. Meanwhile, I am going to keep a checking mine...and will pull the plug when thinnest pad gets around 0.6-0.8mm.