Tire Pressure is a fine line between Comfort, Rolling Resistance and Flat Resistance. Too low a pressure and the tire will move under your weight and the possibility of a snakebite flat will occur. Too high a pressure may make the tire creep off the bead in the worst case and also make the ride of the bike a little harsher than it should.
I am a firm believer that the tires and tubes on my bikes be of the highest quality. I look at the thread count in the construction and like to see a higher thread count if at all possible. On my Recumbent, it runs 20 inch tires and has to support a lot of weight in a small diameter. I run a tire on that which will accept 110 psi, and I run it at that pressure. At this pressure, my contact patch is about a 1/2" wide with little squat in the tire.