By default Mac Time Machine will auto backup every hour if auto backup turned on. I am not really appreciate that frequent hard drive rolling. So here is how the interval can be changed under Lion.
I use Terminal and vi to do the change, you can use TextEdit as well.
First, navigate to /System/Library/LaunchDaemons and open file “com.apple.backupd-auto.plist”. (copy the file to other location first if needed for backup)
Second, find the lines like below:
The value 3600 = 60min * 60sec is the value of an hour. Change the one to whatever you want. I changed it to 60sec * 60min * 24hour * 14day= 1209600 sec.
Third, save and exit the file.