I think proper and frequent monitoring of tyre pressures will make the bigger difference, but I do feel that nitrogen does help keep tyre temperatures and pressures a bit more consistent, the main thing is that you vastly reduce the chances of moisture sitting in the tyre. Yes, professional racing tyres use nitrogen, and so does commercial and military aviation.
But, something to remember is that when your tyres are inflated with nitrogen, it is never going to be pure nitrogen since they would then have to fit the tyres onto the rims in a nitrogen filled room, good luck finding this in your local fitment centre, but you still limit the chance of moisture other than the natural current air humidity.
Tyres are porous which means that over time gas particles can and do escape and oxygen being less dense than nitrogen does escape quicker, so after time you do end up with mostly nitrogen - problem is that moisture is does not escape, so I understand it...