Currently I work out six days a week. Five of those days I do 30 minutes of intense cardio (alternating among bike, climber, running, elliptical) preceded or followed by ten or fifteen minutes of strength work (stuff from your book). One of those days I do non-stop 45 minutes of strength work, also from your book. One day I rest.
As you know, my goal is optimal fitness. I have read some articles suggesting that working out four days a week rather than six is better for optimal fitness.
What is your opinion?
--the more intensely you train
--the older you are
Everyone is different. I would say that a quality training program needs to be designed around rest. Rest is more important:
--the longer you go between unloading days (or unloading weeks/months/years)
--the less your background in regards to a specific training protocol
--the more stress to which you are exposed
The better one takes care of their body (via the Six Foundational Factors of Health--http://triumphtraining.com/blogs/blog/6363808-the-six-foundational-factors-of-health
), the greater threshold that person will have for any stress, including that which comes from exercise.
Could 6 days be perfect for you--yes. But so could 4. And it likely depends on a host of different variables, so I wouldn't get too attached to any specific periodization scheme. Instead, I would listen to your body.
My instincts tell me that you are possibly utilizing intensity more than is optimal. Variety of intensities would likely serve you better and probably result in harder hard days because you're rested enough to truly push the envelope. I also would encourage you to add a day of active rest where you benefit from movement but at a level of exertion which keeps you anabolic rather than catabolic--breathing through the nose only, no muscular burn, minimal increase in HR.