I compared my MacBook retina with someone I know who's had their MacBook retina for about the same time frame 6 months. Their battery life is still hovering around 8717 mAH with 12 cycles while mine is around 8450 mAH with 47 cycles. Granted my battery was also around 8700 mAH when I first got it but now its dropped a bit. I can't imagine why the difference is so significant. I do game a lot on windows bootcamp so maybe all the heat wears out the battery ?