There seems to be little information about the way activation system works in Windows 8, especially for consumer versions of Windows (Core/Pro, not Enterprise). I already know that Microsoft now requires you to enter a key before even starting the installation process, and that it tries to connect to the Internet and activate this key as soon as possible.

Sometimes, though, you don't have Internet connection when installing Windows 8. What then? Can you install Windows? Can you use it? What are the limitations? For how long can you keep your copy of Windows usable without activation?