The actual exam is really, really, really easier than the K&B mock exams, so long as you understand the concepts.
Here's my story:
I have not used Java much, only on a few applications, so i did not have much knowledge of the syntax and never used Collections/Generics before.
I read the K&B book at the beginning of the year so i can get SCJP. I made notes on everything that i did not know.
After reading the book i began Uni semester and did not have much spare time so put off my studies for SCJP.
During mid-semester break (2months later) i read the K&B book again, looking over my notes and removing everything i could remember and making some new notes.
I didn't have time to study mocks so i put the actual exam off while focusing on uni work again.
After 4more weeks and nearing the end of uni i made a booking for the exam because i wanted to start applying for jobs and have the SCJP on my cv.
In the two days before the exam day i spent 27hours cramming study in.
I re-read (skimming over) chapters 7-10 because those were the most difficult for me since i have never used any of the topics myself.
I then done the chapter questions for all chapters, this is probably the 4-5th time i've gone over them so i have memorised a few of the answers by now.
Some of the questions i still got wrong though, but about 90% correct from them questions.
I then did mock exam A and B (from K&B) both open book mode and I think i would have achieved about 50%.
I did A, B, A, B open book mode. Second time around i got most of the questions correct.
Then after 5hours sleep and being up studying for the last 11hours i had to do my exam.
86% (62/72)
So as you can see i did not put as much effort in as a lot of other people but still passed with a good mark (even though mark is irrelevant).
The most important thing i would say is understanding the concepts. If you get a (mock) question wrong, make sure you understand why you got the question wrong even if it takes you 10minutes.
I had the promotional second chance offer so i was not too worried about failing when i went in. I understood all the concepts but the thing i was worried about when heading to the exam was syntax, primarily for collections.
However there was only a few collections questions (maybe 4) and i think 1 generic-specific question when i did my exam. Maybe im just lucky though that my weekpoints did not come up.
Don't stress and good luck