Reconciling continuous peripheral awareness with the moments of consciousness model?

Up to at least Stage 4 (I haven't read past that yet) Culadasa stresses that peripheral awareness should be maintained along with the sustained attention on the breath. However, in the Fourth Interlude, he says that any moment of consciousness is either a moment of attention or a moment of peripheral awareness. How, then, does one sustain peripheral awareness without constantly dividing attention? Should I just avoid suppressing peripheral awareness? Or does peripheral awareness fade naturally at a later stage?