How long should tires last before they dry rot?

ron.dittmer wrote:
I thought the advantage with nitogren was for psi stability. Hot or cold it's the same. Am I right?

That could be true, but they told me when I picked up my rig from the tire shop with new BFGs, that they are less likely to lose pressure over time like air would. For another $10 per tire, I took the chance.