Level of difficulty increasing with each pass of SAT Math Prep practice sections?

I'm doing multiple passes of the practice SAT Math Prep questions in order to reinforce the concepts through repetition.  But, after each pass, it feels like the level of difficulty is increasing significantly and I'm spending more time trying to learn new concepts and less time revisiting those concepts in which I want to improve. Is anyone else experiencing this? With the test just a few days away, I want to make the best use of my time, and just ramping up the difficulty of the practice questions is not what I wanted to do. Thanks!