My 2013 ES came with nitrogen filled tires. It seems that nitrogen does help with the change of seasons. I have not had to adjust the pressure since January 2013. My GS with air needs adjusting with the change from cold to hot outside temperature changes. But as you, I would not pay for it.

 

When I bought my ES in June 2013, the dealership's practice was to do a nitrogen fill in all of the cars in their inventory and to add $100 to the price of the car. When I said that I would not buy the car if I had to pay the $100, they deducted it from the price that I paid. I'm assuming that they didn't take the nitrogen out of the tires and put in regular air.

As we moved from the summer of 2013 into the winter, there may have been a difference with regard to how much air I had to add as the temperatures dropped, but, if that was the case, it wasn't big enough for me to notice the difference, and I still had to add air a few times as the temperatures progressively dropped. According to what I've read from tire experts, with nitrogen, the amount of pressure increase or decrease with changes in temperatures still runs about 2/3 to 3/4 of what it would be with plain air. And, since plain air is already 80% nitrogen, I'm not sure that I'd expect the nitrogen to make any more difference than that.