In your example, 60 PSIG is adequate for loading up to the manufacturer's GVWR and rear axle GAWR. If you are not running over these manufacturer's limits, 60 PSIG is fine and will ride a lot better.
With our dually, even pulling a 16K 5th wheel, we can run the pressures listed on the driver's door sticker of our truck when towing with no problem. In this case, all it would accomplish to air the rear tires up to their maximum rated pressure is to promote center tread wear and make the thing ride like a logging wagon.
2016 Ram Longhorn 3500 Dually 4x4 CCLB, 385/900 Cummins, Aisin AS69RC, 4.10
2014.5 DRV Mobile Suites 38RSSA #6972
Come join us on a TEXAS BOOMERS