When vehicles are operated on normal roads it is always best to follow the inflation pressures in the owners manual...anything else and you are setting yourself up for a potential problem.
With that said here is some more info to ponder....
When a vehicle manufacturer selects a tire size for a vehicle, they evaluate the vehicle's gross axle weights, the anticipated use of the tire, and the tire diameter and width. If inflation pressure has varied from that which was recommended by the manufacturer, it's likely that the tire's wear and performance characteristics have also changed.
Under-inflation
If your vehicle's tires are under inflated by only 6 psi it could lead to tire failure. Additionally, the tire's tread life could be reduced by as much as 25%. Lower inflation pressure will allow the tire to deflect (bend) more as it rolls. This will build up internal heat, increase rolling resistance. The smaller the tire, the faster the heat builds up.
Over-inflation
If your tires are over inflated by 6 psi, they could be damaged more easily when running over pot holes or debris in the road.
Effects of Time and Temperature
Tire inflation pressures change due to time and temperature. Tires lose about 1 psi per month due to air escaping through the rubber as it stretches. If you were to check your tires only every six months, it would not be uncommon to find them under inflated by as much as 6 psi. Tire inflation pressures also fluctuate with changes in the outside air temperature. This occurs at a rate of about 1 psi for every 10°F (plus or minus). So the tires you set correctly with an 80°F ambient temperature will be under inflated by 6 psi at 20°F.
If you add the variations of time and temperature together, it is easy to understand why a tire's inflation pressure should be checked frequently. Improper inflation can cause tires to wear irregularly and can void manufacturer's warranty.
For even more info...
https://www.rma.org/getfile.cfm?ID=432&type=publication