Perhaps I’m wrong, but I doubt anyone can configure their machine to always max out its resources for every render. Some renders aren’t going to need as many resources to compute their data. Processors and RAM aren’t the only variable when rendering either. Your hard-drives can only spin and write data so quickly (keep in mind your system is also probably using hard-drive space as a scratch disk also). There will be a threshold where one (be it RAM, processors, hard-drive, graphics card, etc.) cannot keep up with another.
That being said, I imagine someone may have some tips on maximizing your settings to get the most out of your resources. I’m still trying to figure out the best configuration for my computers also.