So, tires don't oxidize; they dry out, which causes cracks and checking.
The plasticizers used in their construction are cooked out by solar radiation (UV to be specific - the same wave lengths that cause sun burn and skin cancer in humans). (COVER THOSE TIRES) I also use 303 UV Protectant to treat the surface of all my tires. (Patent US2721185 - Vulcanized liquid polymers as rubber plasticizers - Google Patents
The AMOUNT of plasticizers used during the Vulcanization process depends on the intended use; speed of rotation; and estimated frequency of use.
The LESS the tire will be used, the more plasticizers are added which makes the tire more flexible and wear faster; BUT they can sit for 11 months and then be spun up to 65 MPH without blowing up. They can be twisted without failure due to that flexibility. ST tires are made this way.
The more often the use, the less plasticizers are needed as they circulate between the molecules of Vulcanized rubber during use. Less plasticizers make the rubber more stiff and wear longer. LT tires are made this way.
When infrequently used tires flex during use, the dry rubber on the OUTSIDE surface will crack and check (small cracks). The most flexing occurs at the tread and the cracks start between the treads. This is bad because by the time you see cracks on the side, you can guarantee there are more severe ones you can't see. To say they "fail from the inside out" is a myth unless you hit something and break a belt; they fail from the outside in until they deflate (typically "at speed" - maximum tread flex).
A case can be made for Nitrogen in race car and aircraft tires due to the extreme fire risk at the speeds their tires turn. An minor brake fire can become a bomb when fed with Oxygen in ANY amount under pressure. This is not the case in a motor vehicle.
Just think about it.
Race cars tires, 200 MPH plus from a standing start.
Aircraft tires; Zero to 180 MPH in SECONDS
Space Shuttle - Zero to 250 MPH in SECONDS.
Does that fit your driving pattern?
The "Molecule Size" argument is equally silly;
I check my tires every time I move the camper and carry a small compressor to top them off when needed. What do I care if I need to use it once or twice a year. Most often it is temperature or pressure changes in the ambient atmosphere cause a much greater need to change the tire pressure.
Put the camper away in August and then check the pressure in January.
OMG the air leaked out!
No, that is just Boyle's Law of gases at work. The interior Volume of a tire is fixed (even when it flexes), so any temperature change will move pressure.
The air is still in there; it just won't support as much weight due to less "vibration energy" in the molecules.
Fill it up to the correct pressure in January, then check in June, you will need to let air OUT because the more energetic molecules will raise the pressure in the tire.
Long tire life on a camper is a result of the proper tire for the job, run at the correct pressure for the load carried, and operated at the rated speed for that pressure and load.