I have been using the Windows 8 Enterprise for several months this way for testing rather than backup my data and reinstall the OS just to reinstall my applications, followed by configuration tweaks, which can be time consuming. I have started extending the trail to give me more time.

The process of extending a trial is called ‘rearming’.
Here is how I have done so:

  1. Open the command prompt as (Admin) | Answer Yes to the User Account Control
  2. You can then check your license information by typing slmgr /dli – this provides information on your version and license status.
  3. You could also use the command slmgr /dlv for more detailed information – good to give you status of how long you have before complete expiration of your trial 

If you just want the expiration date info type: slmgr /xpr

And finally what you have been waiting for: The rearm command.
Like the ones I mentioned above all you need to do is type: slmgr /rearm then reboot the computer.

This can be done no more than 3 times of the life of the install of the Windows 8 system. If you time it correctly you could have Windows 8 for free for 270 days. How cool is that.

Info on my test machines:
1 Physical Machine and 2 Virtual Machines (VMware)