Nothing wrong with using nitrogen. You are correct in that the pressure will remain stable, as there is no moisture content in the gas so it is not affected by ambient temperature changes. The only issue is that if they do require topping up, you can only use nitrogen... and that's hard to come by in a lot of places if you're out touring. You can use compressed air if nothing else is available, but then the nitrogen is contaminated and you'll have to start all over.
Also, air is free (if you carry your own 12V compressor), nitrogen costs money.
It isn't WHAT you ride,
It's THAT you ride