You can already have the preview several months before launching the final version, have it available to the developers, prepare everything so that it turns out perfect, so that at the last moment, at its launch, appears one of those bugs that you know at least exists but you do not give how to solve it.
This sequence of events is what has happened with Android Lollipop 5.0, the biggest Android update to date. They just changed their way of releasing updates with a preview so that third-party app developers were up to date at the time Lollipop was released. The only handicap is that the launch has not been as desired by Google, since in the first days the users of Nexus devices found that their tablet restarted by itself, I had lag or some other problem. Today it has been known that Google has solved one of the bugs that brought him the most down the street of bitterness.
Memory leak for Lollipop
This bug is a memory leak that has been present on users' devices that have Android 5.0 installed. This error caused the memory of the device to be loaded and its management was not adequate, which resulted in inopportune random closings of all kinds of processes. These processes include apps such as Play Music or even the launcher.
The devices affected by this bug are the Nexus 7 and Nexus 5, although others have surely been harmed by poor terminal memory management. A curious detail is that this memory bug reached the 1750 stars on the web that Google has to list the list of bugs to be solved, so the solution was a high priority.
Getting better with 5.0.2
Google updated to Android 5.0.2 days ago fixing a good amount of bugs, which has caused the performance of Nexus devices to have improved considerably. In my Nexus 7 2012 the navigation through the interface and through the apps is smooth without any lag, so if Google is preparing to launch the fix to the memory leak bug, the performance will improve considerably.
If already with 5.0.2 a device like the Nexus 7 2012 seems to have revived From its ashes, the next version 5.0.3 (if it were this one) will give Red Bull wings to this tablet as well as the Nexus 5 and other Nexus 7 devices.
Shameful ... it is a shame what is happening with Lolipop ... there is no @ # $% & junk that does not cause problems. What a shit on the part of Google that with the nexus they do that ... I don't even want to think what the Galaxys, Ones, Xperias and others will have ... I tremble for the updates of the manufacturers. I'm going to wait a long time to update my note 4 ...
Painful
Well, I also have a nexus7 from 2012 and it went from kitkat to useless brick mode with system error.