The OpenFX 8u20 release is aimed at stabilization. Over the past few years, many new features have been added to FX that have increased functionality but also increased the bug count. This release is about reducing the bug backlog, improving the SQE pass rate and improving the quality of the code that we already have.
Weekly sanity testing is performed to catch errors early. See Sanity Testing
Milestones are clean points where FX could be shipped. A milestone contains no P1 or P2 issues. Committers are encouraged to hold back significant changes just before a milestone to maximize stability.
Milestones occur at roughly 6 week intervals, starting and ending on a Tuesday. Extra emphasis is placed on testing the week before a milestone and on the Monday of the milestone.