Vista made me a switcher

If you think Time Machine backs up too often (or not often enough) for your liking, navigate into /System » Library » LaunchDaemons. There you’ll find a file named com.apple.backupd-auto.plist. Open it in your favorite text editor, and look for this section:
<key>StartInterval</key>
<integer>3600</integer>
Change the 3600 number to some other time interval in seconds, and you’ll have changed Time Machine’s backup interval.