I've been filling nitrogen into all my cars' tires since 3 years ago & it seldom decrease its air pressure unless punctured. I noticed significant improvements in terms of road noise when cruising in moderate & high speed along highways.

Btw, it does reduce the heat being generated after your outstation trip. Try to feel the difference by pumping normal air to one of the tires in front then another side, fill it in with nitrogen. After a drive to your destination outstation, place your hand on each of the tires mentioned & feel the temperature.

At least I noticed the difference.