I wouldn't bet that the way a file is analyzed by an encoder will secure a definitive result once it's been done once or twice. I think that for lossy formats the rule of thumb of not editing the file too many times, should stand. but maybe I'm wrong about that for at least some encoders? on the other hand, we do know that from an audibility standpoint, it's usually no big deal. some years back I remember people running like a hundred or more encode-decode for fun ... I mean science.