I’‘m not sure if you are referring to dates or processes so I’'m going to answer both.
In general the idea is to release a new version of the server every 2 months (at most). Possible reasons why the 2 months cycle could be shorter are: 1) important bug fixes, 2) new features are available and there is a high demand from the community or 3) new version of Spark or Live Assistant require new features of Wildfire.
The process we follow to release a new version of the server does not involve release candidate versions[/i] unless there are a bunch of new features that haven’'t been fully tested and we need some help from the community to test them. So far we had alpha, beta and RC versions for only one release of the server. The rest of the server releases went from nightly builds to final releases.
The reason for that is that for each new feature that we implement we try to create automated test cases (e.g. junits) when the functionality is also supported by Smack (our client library) or if not we just run manual test cases. Product quality is very important to us so we usually spend quite some time testing our software before making a final release. A consequence of this “development methodology” is that our nightly build versions tend to be as stable as our final releases.