For two weeks Arthur remained in the Duke's Tower to oversee his daughter's recovery, but there was a point he knew she didn't need him any longer. She stopped staying inside the Duke's Tower and was starting to get reacquainted with a set schedule that followed the other apprentices.
Even though Irene couldn't do night watch, she was still keeping to their schedule which meant that she was awake when Arthur mostly wasn't. Their awake windows started overlapping less and less.
What further forced Arthur's hand the most was the snow that started falling. It was light but foreshadowed how harsh that winter would be. He needed to get to his wife and youngest child and ensure that they were set for the winter considering he had neglected them for the duchy. It was time to truly part with his daughter for a while.
