As stated, lowering the pressure lowers the boiling point. If you can get away with that, it is likely that you live in an area that doesn't stress the system much. Or you have a rig that doesn't. The AC swap that caused the overheat I mentioned above was a manual rig with no AC and the owner had no issues with his compromised system. Subpar radiator, muddy coolant, and I'm not sure that what was in the radiator was even anything but water. The thermostat housing has corrosion under the end of the hose and had swelled the hose so much I had to replace it because it was over 1/8" too large to fit the neck on the new housing. When I say muddy, there was a lot of sediment and the "coolant" was rusty colored and even after the 3 day drive around flush, the inside of the block could have used another drive around flush.Perhaps Mrblaine could answer this.
A common practice growing up and still to this day, as my vehicle cooling systems would start to age and develop a persistent leak,
I would reduce the poundage on the radiator cap which was very effective on my older vehicles.
My only theory was that this reduced the pressure in the cooling system which in return stopped a small leak.
Is this not a good practice as it does appear to prolong the life of the radiator.
My TJ sits with a 13lb cap on a 13yr old radiator.