Microsoft reveals that Windows 10 builds will stop booting shortly after they expire

A Microsoft support engineer recently posted the expiration dates of the current Windows 10 Technical Preview builds, which also revealed that eventually, Windows 10 will stop booting. The process starts with warnings of the imminent expiration. After the expiration date has passed, Windows will spontaneously restart every few hours. 15 days after the expiration date has passed, and assuming you survived that long without having been driven mad by the restarts, Windows will stop booting, effectively rendering your PC OS-less.
http://cdn.winbeta.org/sites/default/files/news/WindowsExpiration.jpg
Keep in mind that this info is related to the Technical Preview, we don’t know whether the same will apply to the final build of Windows 10 but it is likely that it will. The latest Windows Technical Preview (build 10061) expires on the 2nd of October 2015, and users will have approximately two weeks to upgrade before it stops booting.
 
Full Article