First, why is this on the Swap & Sell board???:fire:
It has nothing to do with temperature or alititude. Nitrogen maintains a more constant tire pressure because the nitrogen molecules are larger and do not leak through the sidewalls of the tire as easily. The typical tire filled with compressed air will leak about 1 psi per month.
Also, the lack of air in the tire also slows down the oxidation of the rubber...so that is reported to make the tires last longer. But considering that the exterior of the tire is exposed to air, oil and other contaminates, that probably is an insignificant factor in tire life... However maintaining the proper tire pressure does help prolong the life of your tires.
The real benefit for using nitrogen in your tires would be for storing a vehicle, RV's and boat trailers, etc. that are seasonal, or not used frequently.
Consider that probably more than half the tires on the road in the USA are underinflated. I think getting the operator to even look at the tires and other maintenance items on their cars does more for longer tire wear, engine life, etc.
I would probably never pay to put nitrogen in my tires. I found that the cost of a small air compressor makes it easy to keep the tires inflated and is great for running some air tools and nail guns around the house and garage.
...Rich