I once had some Mercedes where the parking brake didn't hold. So I took it all apart and found the shoes glazed over. They had plenty of material but no friction.

Since I had time to kill I roughed them with sandpaper. This did no good. I finally just replaced them and that fixed it.

While I was in there I remember replacing some hardware since I was in there and it was cheap.

But in what must have been the last fifty years I can remember needing to do this only once. So it is not a common maintaince item.