I still think the semi-rigid foam idea is a lot better than nitrogen, btw. And I'll believe the folks at Consumer Reports over the ones on this site that claim nitrogen doesn't leak down, or leaks down much less than "air". CR filled a bunch of tires with plain old air and with nitrogen, then let them sit for a year. The results, if I remember correctly, were that all the tires lost some pressure, and that the pure nitrogen filled tires lost about one psi less than the plain old air filled tires on average. They considered it to be an insignificant difference. I consider it to be a significant example of why it makes no sense to pay for nitrogen.
One of the things that bothers me about all the hyping of nitrogen is that it just encourages more people to neglect checking and properly maintaining their tires. There are way too many folks running around who don't check tire pressures until someone tells them they have a flat, and now we have people telling folks nitrogen doesn't leak out and doesn't change pressure with temp changes and various other BS that will lead even more folks to ignore their tires until they have a failure. If life were fair and idiots were only allowed to kill themselves instead of innocent bystanders, I would say let the idiots kill themselves and improve the gene pool. However, life isn't fair and it isn't just the idiots who wind up dead.
Jerry