"Well, I'm not sure," Jon shrugged nonchalantly. "The maesters who had penned the treatises on dragons didn't have many specimens to base them off. And it was merely based on observation rather than understanding and knowledge. As you know, no books survived the Doom, so not much is actually known about dragons. Although it was for the best, feeding Winter had become quite costly in the last few years. While it seems he will not grow bigger, his fire continues becoming hotter, his scales and spikes - harder, and he somehow manages to fly faster than before."