The show runner D.B Weiss touched this topic in this interview on Vulture. I got this link from wic.net. I am on phone and for some reason the vulture website is not loading so I have not read this, so there might be spoiler. Proceed with caution if you don't like spoiler.
http://www.vulture.com/2014/03/db-weiss-on-game-of-thrones-kids-aging.html