So I used to work in aircraft maintenance (never in Russia though) and the policy is to change the brakes when there is $minimum_thickness of brake pad remaining.

There's a little wire embedded in the pad and eventually as the pad wears thin the wire completes a circuit with the rotor, and lights up the aerospace version of the Check Engine Light.

The brakes on these planes certainly have some remaining life but they're technically unserviceable as per the airworthiness policy that Boeing/whomever produced as part of the approved maintenance program for these aircraft.

Whether the Russians follow that policy is another question. When I was in the Air Force we saw lots of Russian military Antonovs and they, uh, weren't in good shape.