I highly recommend *reviewing* the sample projects, as there are useful design patterns to learn and emulate, but the effort involved in refactoring the sample projects to meet the exam requirements is usually higher than writing code from scratch that follows a similar design pattern but directly matches exam requirements. Bear in mind with this exam that it is primarily graded on functionality (50%) and design (30%), with style (15%) and documentation (5%) worth much less. Compare this to the CLD, where style and documentation are collectively worth 25 out of 40 points (62.5%). Your strategy for time management during the exam should reflect this.
I wrote the sample exam for the CLED, and the solution provided is what I coded in 4 hours of time (yes, including the icons). I expect, like MKerry says, that if you could finish the sample in about 5 hours that you're on track to do well on the actual exam. The sample is more complicated than the actual exam.