I started looking over things during my frist summer. But This is my advice:
Dont try to do subjects with lots of memorization, unless you just didnt learn it first year. Example, first year we had biochem and I never learned some of the less known pathways very well(purine, urea, ect.) So you can learn this. The only thing is, YOU WILL FORGET IT. So whats the advantage? Only that It will come back to you easier next time. I dont think the return for your time is as great. I am 5 wks from boards and 1 hour of study now is probably equil to 5 hours that I put in last summer. So you have to ask yourself is it worth it? If I were you, I would Get BRS Phys, and maybe Guyton as a reference and just Study the heck out of it. Get some Q's like Pretest or something and do all of them. If I could do it again, then I would have put all my time into PHYS. b/c you need a good foundation for path and its also important for Boards. Thats my opinion, but everyone will tell you something different.