we just got back from a 3500 mile trip and the tt tires, which are brand new, were fine. but at every destination i checked pressure and lug nut tightening. i'm taking it in for some minor warranty ...
I've forgotten the specifics, but Trailer Life had an article on nitrogen a few months ago. After reading it, I didn't see any need to bother with it, and if I did, nitrogen is not readily available. Like you, I'm constantly checking my tires. At every diesel stop, the first thing I do is walk around the entire rig, placing one hand on the tread and the other on the hub, checking for excessive heat.