You have until Jan 31 to complete the CFA. However, to piggyback on Capt. MJ's advice, DO NOT wait until the end or near the end to take the CFA. I had two candidates do that this past cycle -- waited until January. They were either "too busy" to take it earlier or were "training to do better," Both failed. Neither is an incoming plebe.
For those who tell me they are "still training" in November or December (and they don't look to be obviously out of shape), I have to wonder what they were doing in May and June and July and August . . .
Practice the test in real time. As soon as you are confident you can get decent scores, take it for real and submit them. (You can get a sense of passing scores by searching CFA threads). If you think you can do measurably better, then keep training, have your scores zeroed out and retake. BUT . . . get a passing score on the books and only retake if you are confident you'll do a lot better. (IOW, if you only do one more crunch or run the mile 10 seconds faster, there's risk in retaking that you'll do worse, so don't do it).