tony,
I would think that earlier studying to shore up conceptual stuff you didn't learn well the first time or want to review to reinforce might work out just fine. I'm doing this now with subjects I've historically sucked at, like biochemistry. I don't expect to be able to map out any of the pathways three months from now by memory, but when I get ready for that intense preparation at the end I do believe the framework will be there within which I can anchor the details.
Here's one way to look at your situation... There are two aspects of USMLE preparation (following Goljan): memorization, and understanding. There are certain things you just have to memorize (anatomy, DOC lists, some adverse effects, a lot of micro, etc.) and then there are places where you must ask "why" a certain thing happens (lots of physio, pathology, and even some biochem for example).
Learn the "why" now and the "what" later. Why do anticholinergics have certain side effects? Why don't treponema gram stain well? Why do certain toxins produce watery diarrhea? When you start the intense memorization later of the huge "what" lists, hopefully the underlying comprehension will still be there and help to solify that condensed learning.