Hi Kathy,
I agree with you that quizzes are good while learning, but full exams are better to improve within a couple of weeks from the real exam. They helped me understand how to deal with time management and become a good proxy of the real exam, including tension and a bit of anxiety - at least for me.
For example, after taking a few mock exams, I realized I performed better in the late morning than in the afternoon: this was crucial to schedule my exam at the best time for me during the day.
Good luck with your PMP exam!
Gabriella