The support life cycle for Microsoft products has been adjusted so that products leaving support can benefit from the latest patches. The change, effective Jan. 2006, was first applied to Exchange 5.5 but will become a standard feature of the product life cycle.

Microsoft's product life cycle includes three major components: a five-year Mainstream support phase, during which patches and updates are free; a five-year Extended support phase, during which critical security updates are free but other updates require an Extended Hotfix Support Agreement; and Online support, which runs concurrently with Mainstream and Extended support and typically beyond it. (Mainstream and Extended support phases may be longer than five years in cases where more than three years come between product releases.) Business products are covered by all phases, but consumer products are not eligible for Extended support.

Under a new policy, when a product leaves its final support phase, the last date of support will always fall on a "Patch Tuesday," the second Tuesday of a month. The new policy ensures that any known problems with a product can be addressed with patches released in Microsoft's normal monthly patch cycle.

For example, Extended support for Exchange 5.5 was scheduled to end on the last day of 2005. However, Microsoft extended support to the following Patch Tuesday, Jan. 10, 2006, enabling it to release a final supported patch for the version on that date. The patch itself is supported until Jan. 31, 2006. (For more information about the Exchange update, see "Jan. 2006 Security Updates".)

The Microsoft support life cycle policy is outlined at support.microsoft.com/lifecycle. This site will be updated over the next three months to incorporate adjustments to the end-of-support dates.