Will it make the tires last much longer?

Why was I told this?

Will it also make your tires more prone to blowing up if they are older than recommended?

I worked for two major tire manufactures for about twenty years. A significant part of that time I was involved in quality control.

One of the tests we performed was to measure the amount of rubber actually coming in contact with the driving surface. This was done by inflating the tire to design pressure and applying the design load. If your vehicle always weighs the design load you will have maximum contact surface at the design inflation pressure.

It is unlikely that your vehicle always weighs the design load. Too many variables like number of passengers, amount of fuel, and the junk in the trunk affect weight. The vehicle manufacturer (VM) selects the tire based in part by what they expect will be the usual load. Like much in life it will be a compromise.

The VM does know the exact weight of the vehicle AND the best guess at the “on the road” weight. Go with the pressure on the “door post” and maybe make slight adjustments from there.