Stable kernel updates

3.18 and 4.10 (presume a typo) while already marked EOL were always maintained by Greg, and so he is probably backporting the fixes he gets as a "freebie" (most likely without any implied warranty), all other kernels you mention have a different maintainer[1] and therefore you should expect their releases to be done at different times and through a different announcement

[1] https://www.kernel.org/releases.html