I strategically took the DAT right after I completed Organic Chem 2 - so I had also just finished the Bio sequence and was in Genetics along with molecular biochemistry.
So I really did not have to study for Organic Chemistry/Gen Chem or Biology that much at all, and I focused on the sections that I needed a boost in like the PAT. I got lucky because my timing was such that I retained all the learned information from Biology and Chemistry. I feel that the difficulty of my school prepared me more than anything for the DAT.
That aside, I would not over do it. Try to study in 1 to 2 hour bursts throughout the day, and take a break inbetween sessions.Most importantly, take practice exams in real conditions. Nothing will prepare you like the real thing.