One of the more visible aspects of Windows as a Service is that Microsoft has been learning as it goes along, and didn't come straight out the gate with a clear vision of precisely how Windows updates would be delivered, or when. Initially the plan was to push each release out to consumers as the "Current Build" (CB), and a few months later bless it as good for businesses, as the "Current Build for Business" (CBB).

A clearer plan has been crystalizing over the last few months, first with the announcement in April that Windows and Office would have synchronized, twice-annual releases, and then June's announcement that Windows Server would also be on the semi-annual release train.

Today, Microsoft has put all the pieces together and delivered what should be the long-term plan for Windows, Windows Server, and Office updates. It's not a huge shake-up from the cobbled together plan before, but the naming is new and consistent.

Windows and Office will each have two release channels: a Semi-Annual Channel, which replaces both CB and CBB, and a Long-Term Servicing Channel, which replaces the Long-Term Servicing Branch.

The Semi-Annual channel will be released twice a year, in March and September. Retrospectively, Microsoft has deemed the Creators Update, version 1703, as the first SAC release. The next SAC release will be version 1709, branded as the Fall Creators Update. Each SAC version will receive 18 months of support. These overlapping support windows mean that enterprises can still hold back each new SAC release for a period of time until they're confident that it's safe to release, but it doesn't appear that there will be the same formal delay as existed with the CB and CBB pair.

The Long-Term Servicing Channel will be released every two to three years. The last such release (still under the LTSB naming) was version 1607, the Anniversary Update. The next isn't due until 2019. These releases have the traditional 5+5 servicing that Microsoft used under its old development model; five years of mainstream support (where both security and quality issues will be addressed) followed by five years of extended support (where only security issues will be fixed).

This matches the terminology and servicing policy already announced for Windows Server. Office will follow the same pattern.

The positioning of the two channels is much the same as it has been since Windows 10's release, but perhaps with Microsoft being a little more unambiguous about it. Microsoft believes that SAC should be used on almost every machine, whether it be consumer or corporate. LTSC should be restricted to "special-purpose" machines, such as those used in point-of-sale systems or medical or industrial equipment. LTSC is only available through Software Assurance, and only for the Windows 10 Enterprise variant. In other words, Microsoft doesn't think that enterprises, even conservative enterprises, should be using LTSC on their corporate desktops at all.

Rather than using LTSC, Microsoft says that corporations should have a rolling six month cycle with three phases; a planning stage, using the Windows Insider program (which was extended earlier this year to better handle the demands of business users), an initial deployment stage, during which pilot users pick up each new SAC release soon after it is available, and then a broader deployment stage during which the SAC release is rolled out to the rest of the organization.