from my uni days I dimly remember that brand new brakes do not perform as well as brakes that have worn in. This is because with brand new pads you have uniform pressure across the pad and the inboard part of the pad does not provide as much braking effort as the outboard part. To provide the maximum retardation you have to wear the pad so that you have uniform wear across the pad and it will then provide the maximum braking effort. From the point where they are worn in to almost worn out they should provide the maximum braking effort possible.
before someone shoots me down, this is a dim memory from almost 200 years ago when I was an undergraduate at Birmingham and much of that time is rather hazy...