You can increase the time between Time Machine Backups by editing the following file from the Terminal.
sudo vi /System/Library/LaunchDaemons/com.apple.backupd-auto.plist
The following line is the time between backups in seconds. Change it to whatever you would like the interval to be.
<integer>86400</integer>
I changed mine to 24 hours or 86,400 seconds. You will likely need to reboot for the change to take effect.
