At a post on Microsoft Answers, RajithR, a Microsoft Support Engineer, posted the license expiration dates of Windows 10 Technical Previews, build-wise. He has summarized the expiry dates for each of the Windows 10 Technical Preview builds that Microsoft has released so far, in the form of a table. Two weeks before expiry, Windows 10 Technical Preview will give warnings. On expiry, it will reboot every 3 hours. After 2 weeks, your system will no longer boot.
Windows 10 Preview license expiration dates
|Build number||Expiration warnings begin||License expiration date||Windows will stop booting|
He has mentioned that approximately 2 weeks before a build’s license expires, Windows 10 will start giving warnings, asking you to update to the latest Technical Preview build. If you are receive such expiration warnings, it is quite possible that Windows Update may be failing to install the latest Windows 10 Technical Preview build automatically. You will then have to download the latest ISO file from Microsoft, mount it and launch setup.exe.
Once the build expires, your computer will automatically reboot every 3 hours.
The computer will no longer boot, 2 weeks after the license has expired. In this case, you will have to download the ISO file from another computer and then transfer the ISO file to some installation media. Once you have done this, you will have to boot the computer from the installation media to install the latest build of Windows 10 Technical Preview.