Tommy M:
I know your question is theoretical, but I wonder if perhaps that questioning would be better applied, and likely more useful and informative, to what it is to be aware in this moment?
I actually see this as a very practical question. I'm talking about people claiming to never go unconscious, i.e. they are continually conscious during sleep, during the moment of shifting from awake to sleep, from dream sleep to dreamless sleep, if for some reason they faint, they're still conscious (and they can realize that they just fainted) etc.