Mountain Lion: OS X Mountain Lion has a handy automatic update system, but unlike previous versions of the operating system, you can't set the frequency of updates. If you want to update more (or less), OS X Daily shares a simple Terminal command to allow you to control the process.
With all types of vulnerabilities getting patched by Apple all the time, the default behavior of searching for updates once a week might not be enough for you. To change it, launch Terminal (Applications > Utilities) and enter this command:
sudo defaults write /Library/Preferences/com.apple.SoftwareUpdate ScheduleFrequency 3
The above example changes the software update check to once every three days. You can change that to any number you like for more (or less) frequent checks.
Change the Software Update Frequency in OS X Mountain Lion | OS X Daily