172 Cup rear brake effort

[Keyser Soze]

My brakes feel like they work fine but looking at the rear discs there are signs of corrosion on the face.
There's plenty of meat on the pads.
Is this normal?

 

[stevescort172]

iirc they are only doing 5-10% of the braking effort, same as mine mate it could go years without needing a set.