The life cycle of a kernel release

Week 0: the merge window opens
All new features and significant changes merged
Typically several thousand patches

Week 2: 2.6.x-rc1 is released
The merge window closes - no more features
...usually
Patch rate remains high
but they should all be fixes

Weeks 3-8: additional -rc releases
Patch rate slows as bugs get fixed

Week 8: 2.6.x is released
2.6.x.y bugfix releases follow later