Mac: By default, a Mac checks for software updates once a week. If you want that check to happen more (or less) often, you can change just how often your Mac checks for updates with a simple command in Terminal. Open up Terminal (Applications > Utilities), and type in the following command, substituting the 1 at the end for the number of days you want to lapse between checks (to check once a week, it'd be seven, once a month, it'd be 30 and so on):
defaults write com.apple.SoftwareUpdate ScheduleFrequency -int 1
That's it, tap Return and you've changed the update frequency to whatever you prefer.