B&T,
I agree with you, I usually run about 60 or so and keep my tires at the max rated PSI on the sidewall. I'm just not one to push the envelope by adding a few pounds of air and speeding up. I am just fine tooling along watching the scenery and not feeling like I'm forced to push the limits to get there a couple minutes sooner. I haven't found anything (other than grand kids) that would justify wanting those few extra minutes, and after being with them for a day or so, I am sure you know the outcome of "wanting to get there faster"
As for that ambiguious statement about exceeding the maximum pressure. You might be interpreting it "ambiguiously"
What it says is that the pressure must not exceed the maximum recommended load PSI rating (plus 10PSI) so, if you're using 13, 14 or 15" load C tires, the max load PSI is 50 so you couldn't exceed 60PSI. however, if you're using 15" load E tires or 16" load E tires, the max load PSI is 65PSI so you couldn't exceed 75PSI. Those maximum increases are based on whether the "wheel" or the "rim" is rated at the increased PSI.