Time Machine backs up files every hour, and if you’re a power-user who updates and saves lots of files (particularly large ones), Time Machine could theoretically never stop working. The problem is that for many users, the Mac can get bogged-down while backing up, in some cases to the point of being unusable.
Thankfully, Stefan Klieme wrote a simple piece of software called TimeMachineScheduler that allows you to easily adjust the backup interval of Time Machine. With TimeMachineScheduler you can set the interval from one to 12 hours, limit backups to WiFi or hard-wired connection only, skip backups during specified hours, and more.
TimeMachineScheduler is free (donations welcome) and works with OS X 10.5 or later on Intel Macs. Because my particular workflow doesn’t require hourly backups, I love this little utility and the features it offers me.