I couldn't leave Hermione all alone, and I thought Harry would have tried to get word back to her, once he was more settled, so combining the two seemed like the right approach. It had also been taking ages to write this story, because I wasn't sure how much I wanted it to cover. When it occurred to me to make the message to Hermione an epilogue rather than a companion story, it gave me a way to tie up my loose ends without writing the rest of the war. :-)