Changing the Time Machine backup interval

By default, Time Machine runs and backups up every hour. If this frequency does not suit you, you can change it. The interval is controlled in a file called "com.apple.backupd-auto.plist" which is here

/System/Library/LaunchDaemons.

Look for a section

StartInterval

3600

I've found the editing it in a text editor makes the file go funny, so easiest of you use Property List Editor from the Developer Tools kit. Its in the applications/utilties folder