In the aviation industry, we would get some training on this issue from time to time, both theory and practical. Primary reason for Nitrogen in aircraft tires is because the nitrogen we purchase is moisture free, often from liquid nitrogen carts depending on where you're working. We maintain nitrogen servicing equipment anyway for servicing struts, accumulators etc because of the moisture free aspects, and because it's and inert gas that won't cause corrosion on internal components. It only makes sense to use dual purpose equipment to service those items and the tires being as how it's expensive to use compressors with quality moisture removing capability.
As for tires leaking down slower etc. all the studies I've seen showed the theory didn't really pan out in the real world, and even after a high pressure tires were left sitting a year without being touched the difference when compared with standard air fill tires was only a couple PSI, virtually insignificant. I haven't seen any studies where it made any difference in tire life, but in theory it regular air could lead to corrosion of the wheel more than you would get with pure nitrogen. Other than tires filled with the liquid seal stuff I've never really heard of wheels corroding out internally.
