This depends largely on how you make use of your computer. Many of our users perform a cleaning around once a day to once a week, depending on how heavily they’ve made use of their computer.
Most of the data that CCleaner is designed to clean is generated by browsing the internet. As such, if a computer hasn’t been used much for browsing during a day, then it probably doesn’t need to be cleaned, for instance.
Conversely, we do recommend closing your browser and performing the cleaning after visiting banking sites or performing other financial tasks online (ecommerce, stocks/investment, paying bills, etc). This will help prevent these details from being accessible to spyware or other malware.
The paid versions of CCleaner (Professional for home users, Business for businesses or other organizations) include several features to help make this more convenient, such as being able to schedule scans to run on a regular basis, or the Smart Browser Cleaning function to allow CCleaner to automatically clean your browser after closing the browser - in this case, you can allow the software to clean as configured.
With a conventional hard drive, there should be no harm in cleaning more often than strictly speaking necessary, but you may wish to be more conservative about cleaning solid-state drives, or other Flash-based storage, as their lifespan is based on the number of writes that any part of the drive can withstand.
As such, cleaning a reasonable amount should be well within the intended usage of these devices, but still, the less frequently that cleaning is performed, the less it will affect the drive’s lifespan.