More questions about patch management

[steve at rueb.com (Steve Bergman)]

My original understanding was that only security patches get issued
between quarterly  releases.  But that then the distro gets updated with
bug fixes 2 to 4 times per year.

I may be getting this all wrong, but I get the impression that there are
3-4 month periods of quiescence punctuated by short periods (or a day?)
of significantly more intensive patching.

Is that correct?  

Thanks,
Steve