Once you have listener's fatigue you might as well shut down for the night and start fresh the next day. There is also a big misconception about sound absorption. It's good stuff. A lthough, I have never had a team of scientists compare it to orthopedic bed foam for actual sound diffusion and absorption, it does work if you know how to use it. The big misconception is that you need a totally dead room, meaning no sound reflection, and that is wrong.
Acoustic foam is used to control unwanted sound artifacts.
Certain building materials, such as drywall, will allow certain frequencies to pass through them and others to bounce off. Depending on how thick the material is and how well it's insulated will determine which frequencies will be problematic. For instance, if the ceiling in your control room allows 125Hz frequencies and lower to pass through but sharply reflects 1KHz and higher then you will have a tendency to attenuate the higher frequencies and possibly even boost lower frequencies to compensate. There are professional people who can tell you where your problem areas are based on years of collected data and experimentation with different types and thicknesses of building materials, but you can get reasonably close in your home studio if you take the time to listen. If your back wall is less than 12 feet from the back of your head when you are mixing then you should kill it.