And a couple of pertinent comments have been posted while I was composing that. :-) I'm with lonemagpie about the importance of consistency, and lack of consistency is one of the things that will throw me out of the story and make me think that it's Lack Of Authorial Clue rather than deliberate bending of rules. And cdybedahl's comment is something I partly agree with - partly, because I find that I give a lot more leeway to stories whose science was plausible at the time it was written. Doc Smith's cheerful use of the aether doesn't bug me, while it would be book-meets-wall time in a story written today that wasn't a deliberate homage/parody/whatever of old-style space opera.