If Nightblood uses breath, but he's on a planet where that investiture doesn't exist, but another system, but it all comes from the same(ish) source of power (The shards), you would think that the system would adapt so that Nightblade could continue to exist, right? I'm a little rusty on Warbreaker material, but if Nightblood and Vasher came over to Roshar and they did not have source in which to gain breaths (I'm pretty sure relinquishing breaths on Roshar doesn't work like it did on Nalthis, they would have to tap into the investiture of the local planet. It may or may not be an equal exchange rate either. It could take a whole lot/Not a lot of stormlight to wield Nightblood, and maybe Vasher doesn't have to give up his breath per day like he did back on his home world.
Can someone clarify that for me? I know a lot of this, if not all is speculation, but if they can travel to another world, and Vasher alone can survive for 12 years, he's either doing it at a reduced rate of losing breath, if he's even using breath to survive. In turn, you would think that Nightblood is the same way since he very obviously still exists. I am unsure and unable to remember if he was passed to Szeth unsheathed or not, because that apparently makes a world of difference.