Right now, there is no set schedule for new OpenTK releases. There is a rough list of features for each version, which is released when these features are more or less implemented. The main disadvantage here is that it's difficult to estimate when a new version will be ready. Some features may hit unexpected snags and delay other, possibly unrelated, features or bug fixes.
The alternative is to make releases on a steady schedule (e.g. every two weeks). This allows new features and fixes to be released promptly, but the inflexible schedule may cause short-term instability (e.g. release a feature that isn't 100% baked).
Right now, I'm leaning towards the second option. The reasoning is that it will increase testing (catch bugs and bad APIs earlier) and quicken development (at most 2 weeks latency between feature and release). This will almost certainly need stricter development practices (e.g. keep trunk stable at all times, develop new features only in branches), which will cause pain initially, but possibly increase quality later on.
What do you think about this? Do you find a steady release schedule desirable or would you prefer fewer but more feature-full releases? Have you used either of these on your own projects? How did it work out?