I believe the sensors give a 1K km warning.
Once the sensors start to flicker, there is still plenty of pad material left, but you don't want to run them down too far. You will need to replace the sensors when you do the pads too, they aren't a reusable item, plus they are cheap.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.