I would like to share my experience with the SCJP 5 exam.
It took around 4 months for me to prepare thoroughly with all the topics. In the first 10 weeks I tried to cover all the exam topics once. I used to spend around 150 minutes on a daily basis. I had referred the SCJP 5 book by Kathy Sierra and Bert Bates for the first go. Then one of my friend suggested me to go also go through the Java Certification book by Khalid Mughal. This is also a good book which basically covers all the topics for SCJP 1.4 in detail. I referred this book only for the basic topics like Inner Classes, Threads, Garbage Collection, Collections and Strings and StringBuffer. These topics are explained very nicely in this book. Then I had gone through the K & B book one more time concentrating mainly on Ch 6, 7 & 9. This took around a month. I also used to code & test small programs on topics such as generics, Var args and Threads to understand them thoroughly.
During my second round through the K & B book I used to solve sample mock questions. After completing the revision I was confident enough to go and register for the exam at a the nearest Prometric center.
During the last two weeks I had concentrated on the Self Tests of the K & B book. Then during the last week I had appeared for the mock exams from both the Khalid Mughal and K & B book. I scored around 85% marks in the mock exams.