Microsoft says that the Windows 8 team make new builds everyday disregarding whether the builds would be chosen or not for major branch. Microsoft has shared the information when Windows 8 release to manufacturing (RTM) is scheduled for release to OEM partners in early August. The last Windows 8 RTM build which has reportedly been selected as the RTM is build 9200.
An individual asked Microsoft on Twitter about how many new builds does the company make in a day and the Microsoft employee responded by saying we make builds every day and the builds are like matrix of language, sku, 32 / 64 or ARM.

This new valuable information describes the working of Microsoft regarding Windows 8. We can assume that the software giant is also capable of making multiple new builds every day. The builds are fetched to a computer which gives the build their build number along with date and time.
Microsoft is working day and night to finalize the RTM build of Windows 8 which would then be released for OEMs in early August. That build would later be launched for public when Windows 8 would reach general availability milestone on October 26, 2012.
Via: Neowin