No, not as species, as it's known at this point that they a remnant of the Endless.

When you click on "buy population", what happens in your opinion? Are they converting living beings into more of them? The description of Stalwarts says that these warriors are "touched" by the Curse of the Lords, which might be either metaphorical or literal. In the latter case, it might imply that they actually were mortal living beings until recently, and then were turned into Dustsuckers. :) 

I've read somewhere a theory that those blu lights at the top of their spires might be a well of souls or something and that the process of binding a soul into armor might require dust. Once that armor is broken, the soul returns into the well, ready to be rebound again later, but however fascinating this theory might be, it would mean they were effectively immortal as long as there is dust and the spire containing the well of souls, but I've never found anything that might prove it, so it's more likely a head-canon of someone else as obsessed with lore as myself. :) Also the BL are quite preoccupied with the current state of their civilization, if they were immortal on a planet full of dust they might have a more optimistic take on their situation.

Anyway I couldn't think of a better place to ask for some other opinions regarding this topic. Any thought?