Not sure why you would run knobbies in the dirt at MAX pressure. I would rather spend $84 on a tire, run it at 13-16psi and get better traction and handling.... and lesson the risk of crashing (sliding out, bouncing off the trail etc) ....... which then might end up costing you more than the $84 to replace a tire more often. Don't ask me how I know this :-)
Putting the knobbies on the street, different story. Put those pressures up to 20-25psi and ride on.