Hunt when the birds are in the milo.
That said, different milo fields I hunt have birds in them at different times. I have gotten birds up at sunrise, in the middle of the day, and in the late afternoon. The biggest thing, to me, is don't have dogs running through the milo. That spooks many out the far end of the field.
Birds see the dog(s) running back and forth across the rows, then are alerted. They just run away, not even having to fly. I have seen that happen many times. I hunt milo without a dog, now, and have much better success.