Microsoft has announced its Product Lifecycle Support Policy for Windows 8. Microsoft offers two kinds of supports to the Windows operating systems - the mainstream support, where it releases security as well as performance or maintenance updates and offers general support, and the Extended support where only security updates are released.
Microsoft is offering extended support for its Windows Vista operating system till April 2017 and till 2020 for Windows 7. Windows XP extended support will end according to Microsoft on 8th April 2014.
This post explains in detail the difference between Mainstream Support and Extended Support.
Windows 8 Product Lifecycle Support
For Windows 8, Windows 8 Enterprise, Windows 8 Enterprise N, Windows 8 N, Windows 8 Pro and Windows 8 Pro N 30th October 2012 has been designated as the Lifecycle Start Date.
Mainstream support for these versions of Windows 8 will end on 9th January 2018 and the Extended Support will end on 10th January 2023, according to Microsoft.