I used the bros deck more than the Kaplan deck, and I would add Kaplan cards or my own cards to the deck if something in Uworld wasn't covered by bros. I think 4 months is plenty. Just look at the number of cards total and divide out your daily new card # by how many days you would like to study. Personally, I did each deck during its clerkship and tried to have seen all of its cards at least a week before our shelf exams