From what I've observed, what appears to happen is that we get 2, maybe 3, minor patches after a major release. Bugs which haven't been fixed in those patches are then held over for evaluation in the next major release. The only way you get a patch after that is if there is a major game breaking bug which kills the game for the vast majority of people (I.E. CTD when approaching a planetary installation).
It's frustrating because I know that if a bug isn't fix by patch 2 of a release, then it probably won't be fixed until the next release. However, from my own software development experience, working on a bug fix work stream and a new feature work stream at the same time is daft and a nightmare when it comes to merge the streams (cue rubbish Dad joke about 'Don't Cross the streams!'). Its a balancing act, if all we got were bug fixes then we'd get no new development and then there would be whinging on the forums about no new content, or if all we got was new content, then there would whinging on the forums about the lack of bug fixes.
So it's a case of do as many bug fixes as you can, while also develop the new content on a single work stream. That way you get less whinging than the other two options. Heck, even if they managed to make a perfect release, that fixed all outstanding bugs and delivered perfect bug free new content, people would still whinge about something.