I would study for less time, more efficiently.
I really think you can study for 4-6 weeks and get the same results as studying 4-6 months.
Be smart with every day. Get through all your material one time, then figure out where you are weak, re-learn those weak areas, start with practice tests and study in between them in your week areas.
An example for you:
I didn't take o-chem 2 before the DAT. I was scoring 16 in topscore less than 3 weeks before my test, I re-watched chad's videos, did flash cards, did DAT destroyer a bunch of times, and got a 27 on o-chem for the real test.
It is not overly difficult material, just need to be efficient in how you cover material.
Another piece of advice is read bio from several sources. Don't use just Cliffs AP. Read Cliffs, Barrons, Schaums, DATQvault and then do it all again. You can read Cliffs and Barrons in 1 day each, Schaums is probably better to read as a supplement for the areas you don't know well and you can do DAT Qvault tests in between. Don't underestimate the value in doing all the questions in the AP books either, they are valuable.
Last piece of advice, get Crack DAT PAT and do 1 test a week the starting about 10 weeks before the test. Take time to figure out why you got stuff wrong, but really just the practice will help you a lot. By the end of it you probably will be getting 4 pts higher than your first test.
Good luck, feel free to PM any questions.