I've said it a hundred times: When I was in school we NEVER finished a text book. Sometimes in the last 2 weeks of school a teacher tried to cover the last 4 chapters, but we never finished a text.
Yet all the homeschoolers every year slave and worry about how many weeks into summer will they have to go to finish all the texts. I got confirmation last week, once again, that even now the conventional schools still don't finish the text books. I was talking with the head of a Math department at a high school. And she was showing me where in the books they usually ended the year (And it was never in the final chapter.)
So yes, you need to finish your course-however you have planned it-but you don't have to finish the text.