Just thought I'd drop my opinion!
I am a junior now, and would not have taken the DAT last year. I'm not sure how your school works, but many of the classes I took just this last semester feel like good review.
Courses like biochem, vertebrate bio, animal physiology, comparative anatomy, histology, and analytical chem are all relevant and can only help deepen your understanding of the sciences. If you have taken these by the end of your soph year, than I guess I can't argue with ya! The only adv you'd have to taken the test now is that ochem is definitely fresh.
Also does your school have any sort of test prep or pre-prof. committee? They probably would have an intensive review next spring if you have one.
Really, since you are already thinking about the test, you could just take this year to really practice up the PAT and get a 20+ which looks excellent on apps. And instead of cramming for 3 months, you could be dissecting the Kaplan/ect books a year in adv. and really have your stuff together come next spring.
Oh well, that's what I'd do if I had your situation.