Probably a lot more than once when you consider that different devices have different capabilities, and that they might stream you different bitrates depending

Probably a lot more than once when you consider that different devices have different capabilities, and that they might stream you different bitrates depending on conditions like your network capability, screen resolution, how much you've paid them.. You could also imagine they might apply some kind of heuristic to decide to re-encode something based on some condition... Like fine tune encoder settings when a title becomes popular. No idea if they do that, just using some imagination.