Microsoft has revealed in a blog post that the preview build of Windows 8.1 will expire in less than four weeks. Microsoft has already rolled out the final version of Windows 8.1 and Windows RT 8.1 on October 17th, so if you are still testing out the Preview build, now is the time to upgrade.
"Thank you for using the Windows 8.1 Preview. Partners should communicate with their customers to make sure they move to the final released versions of Windows 8.1 and Windows RT 8.1 before January 2014 when the license for the preview will expire," Microsoft stated in an official blog post.
Microsoft first revealed the Preview build of Windows 8.1 during the BUILD Developer Conference earlier this year. Microsoft then rolled out the build on June 26th.
If you are one of the few people still running the preview build, you can head over here to learn all about the final build of Windows 8.1 - including upgrading/updating to it.