note: the following is a 'general rant' which is not particularly directed towards the OP
i'm always amazed by people who use the words/phrases "overkill" and "all you need to know". what really would classify as a situation in which one's prep is overkill? since you're never sure (despite all the predictive tests that they can take) what score you will receive, (despite all the predictive tests that they can take), doesn't it make sense to prepare as best as possible to achieve the maximum score possible. for some people, that maximum score is 220, and for some it is 280+ [i'm sure a person with 220 and one with 280+ wouldn't agree on their definition of overkill]. once you receive your score, i think you would rather be happily delighted by performing at (or above) your target than underperforming and spending the rest of your wondering what would have happened if you didn't limit your prep to prevent overkill.
now, to the OP: questions will definitely help you round out your studying. almost everyone does UW, and some people also do the NBME tests (with good reviews).
the period required for hardcore study depends on several factors: (1) your performance in the shelf exams and how long it has been since you have been on the basic clerkships (esp. medicine, obgyn and peds) (2) your target score, and how long it takes you to consistently get into that score range (when you take predictive tests such as NBMEs and UW assessment test) (3) what you mean by "hardcore"? to me hardcore, is anything upwards of 5hrs per day, but that is mere "leisure studying" standard for others.
i think that once you have figured out the answers to these questions, you will be better informed to make decisions regarding your prep.
best of luck
