I need to replace the front discs on a Mercedes-Benz A-Class as they've worn below the minimum thickness. When I measured them, I saw that the pads still have plenty of pad material in them, and it feels wasteful to throw them out. However, I don't know if this is an acceptable practice, even though people replace pads when worn without changing the discs routinely. What is the current thinking on replacing discs and reusing serviceable pads, please?