As far as my PLAB 1 experience is concerned:
A month before the exam, I was tired and bored of studying, since I was well aware of all the questions by now. So I stopped studying. But I did keep my eyes and ears open; since a few of my friends were also studying for PLAB 1, I used to listen to their discussions and respond to questions on Facebook. But I stopped studying myself.
A week before the exam, I took a leave’s absence from work. I was keen on making the most of this time and study hard. But I ended up watching three movies every day during this week. I did study on the final day for an hour. But I realised that I was well prepared, so I did not make any more effort.
It’s not because I was an extraordinary student. It’s only because I prepared for it properly - by focusing on the questions instead of theory.