I like to release on the solstices and equinoxes; it's easy-to-remember ritual. If I miss a release date, I'll usually just reschedule it for the next one. Ah, the joys of recreational software development. :) If someone can help speed things up by relating this to income or a degree, I'm all ears!
The above is my normal spiel, but Flow is in a rather peculiar position. Flow suggests fundamental changes to the Smalltalk system, which are awkward to make with the current collaboration mechanisms. I decided my energy, spare-time though it is, was better spent improving those mechanisms, through another project called Spoon.
Releases of Spoon include Flow, but until Spoon 4, separating Flow from it would require a bit of effort on your part. (This has been done at least once, by John McIntosh circa 2003.) Squeak, the Smalltalk in which I work primarily, is simply too chaotic for its level of organization (and my available time) for me to maintain Flow separately in the meantime. One goal with Spoon is to make it easier to maintain a project like Flow within a larger, chaotic system.
The naming theme here is "major rivers". Minor releases are named after tributaries... Nominations for future names gladly accepted; any river on Earth (or anywhere else :) is fine.