So I've noticed that when my rMBP (Late 2013 model) is sleeping, it's not performing it's hourly Time Machine backups. The machine will back up just fine as long as it's on, but when it's off, it's not backing up at all. I do have Power Nap enabled in the System Preferences for both Battery and Power Adapter. Looking through my Time Machine, I can see that my last backup was yesterday at 5:59 pm, when I closed the rMBP, and plugged it into the power adapter. Then another backup this morning at 8:36 am, a couple of minutes after I opened it up. Any thoughts?