If you like Notification Center, in Mountain Lion, you may also like its "Do Not Disturb," feature, where you can turn off notifications if you're busy and they get to be a bother. There are a couple of ways you can do this: you can Option-click the Notification Center menu bar icon, or you can scroll down when Notification Center is visible, and toggle the slider to OFF.
On iOS, you can schedule this action, but not on OS X. Ben Waldie, writing at TUAW, posted an interesting AppleScript/Automator solution to this. You can create an Automator workflow, and set it to run in Calendar, so you can have the Do Not Disturb feature turned on and off at specific times. It's a bit ham-fisted, to be sure; it uses a defaults write or defaults delete command, then a killall NotificationCenter command, which is essentially force-quitting Notification Center and allowing it to relaunch. The problem is that if anything goes amiss, Notification Center might not relaunch.
It's too bad that there's no built-in way to do this. But this is a good solution for now, if you really want to turn Notification Center off and on at specific times.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20130204230120228