I am coming up on my first tire rotation at Costco, I hope it isn't a 2-hour wait. As far as tire inflation with nitrogen, my Costco lets you do it yourself if you wish.

 

The science of how air and nitrogen interacts with metal is not relevant? Not that I believe everything I read but this seems to work on my wheels.

 

From Consumer Reports ...

We filled one tire per model with air and another with nitrogen. Both were filled to 30 psi (pounds per square inch) at room temperature. We set both tires outdoors for one year, and then checked the inflation pressure at room temperature again.
Both tires lost pressure over that time, but the difference in loss was minimal. The average loss of air-filled tires was just 3.5 psi from the initial 30 psi setting. Nitrogen-filled tires lost an average of 2.2 psi.The results show nitrogen does reduce pressure loss, but the reduction was only a 1.3 psi difference from air-filled tires over an entire year.

 

Costco does not have cylinders of pure Nitrogen to fill tires ... they use a system that provides 95% Nitrogen (+/-) ... plus the tire was not evacuated prior to inflating ... so oxygen has not been completely eliminated. Also from a rust standpoint, one would think the performance of the system dryer (requiring regular maintenance) would be as important a factor.