The chicks won't be 40 days old until Monday, so a few more days until fledging would be the norm. And they can fledge at any time of the day, but overwhelmingly prefer first thing in the morning, not a bad thing as winds tend to be lighter (on average) earlier in the day.
And one of our kids is a real little homebody. When it rained early this evening, s/he ran straight back to the nestbox and tucked up under the roof until the worst of it passed. And s/he is back now, sitting on the north edge of the building watching the world roll by. A few minutes ago, she was lying down on her tummy napping in the back corner of the box again. Very cute and homey!