Here’s the official statement from Adobe’s website
Do I need to be online to access my desktop apps?
No, the desktop applications in Creative Cloud, such as Photoshop and Illustrator, are installed directly on your computer, so you don’t need an ongoing Internet connection to use them.
An Internet connection is required the first time you install and license your apps, but you can use the apps in offline mode with a valid software license. The desktop apps will attempt to validate your software licenses every 30 days.
Annual members can use the apps for up to 99 days in offline mode. Month-to-month members can use the software for up to 30 days in offline mode.
Source
https://helpx.adobe.com/creative-cloud/faq.html
Peter Garaway
Adobe
Premiere Pro