Four years is a long time. Most people only need four years to graduate high school or college for instance. Microsoft launched its Surface tablet running Windows RT about a month ago. When the tablet launched there was no official support policy for Windows RT. Most large enterprise buyers want to know that Microsoft will continue to support a platform for multiple years before they start purchasing and rolling devices out in quantity.
Microsoft has now officially confirmed that it will support Windows RT on its Surface tablet platform for at least four years. Microsoft recently updated its support lifecycle page noting that four-year support period. If you're familiar with Microsoft and its support pledge for most of its software, you might know that typically consumer and business oriented versions of the Windows operating system are supported for five years.
Business specific versions get an additional five years of extended support. Windows RT is a hardware and software combination and therefore has different rules for support for Microsoft. The mainstream Support End Date for Windows RT on Service will be April 11, 2017. That is roughly 4 and a half years from the launch of the product.
Since the Surface tablet running RT is a consumer product, there is no Extended Support End Date. What that support period means in a nutshell is that anyone who purchases a Surface RT tablet be able to get updates until April 2017. It's interesting to note that Microsoft's service window for Windows RT is significantly longer than what Apple has been providing iPad buyers. The original iPad for instance no longer qualifies for iOS updates and it's only 2 1/2 years old.