CCleaner Professional is licensed per computer. This means if you have one license, you can install it on one computer.
Benefits of CCleaner Professional includes the following:
Cleaning across multiple users in a single click
System and browser monitoring
Auto-Updating
First notification of updates, beta programs and special offers
“Complete Cleaning” refers to the ability to clean across multiple user profiles at the same time.
Licenses are valid for one year, so this means that the license, automatic updates and priority technical support expire after that time. The product will continue to function after that time as a free version.
You do not need to uninstall the previous months version before installing the latest one