Hi John,
If you plan to take the exam before it changes on July 1, you can activate the Exam Simulator anytime. There are only 122 days between now and July 1. I found the first couple of exams more difficult until I had got through some of the modules.
Here's a post from Cornelius that gives more information about the 90 day activation:
PrepCast Elite
I did a 40-question quiz each day, Monday–Thurday (untimed), and took 200 question tests on Saturdays. It's important to review your answers, particularly the ones you got wrong.
I wish you the best, John!