When planning your PHR or SPHR exam preparations, 14 weeks is your goal. Fourteen weeks of studying and immersion. In the big scheme of things, 14 weeks isn't a long time for a successful exam experience.
You clearly have a baseline of knowledge that marks you eligible to sit for the exam, so your goal in the 90 or so prep days is to expand your knowledge of the areas that you already are comfortable with and expand your familiarity with the areas in which you may be less familiar.
You also need to become aware with the exam experience because you may have not sat for a test in several years.
If you have less than 90 days to study, accelerate your plan. You can make some of these adjustments to your plan:
Consider one week per functional area rather than two.
Focus on the areas with higher exam concentration.
Wake up earlier or stay up later if necessary.
Study at unconventional times, such as listening to audio resources while driving or reviewing flashcards during meals.
Regardless of your availability to study, dedicating yourself to performing well on this exam is an investment that you make in yourself.