I do not care much what other projects do. Postfix has a good record for quality, stability and compatibility, and it supports four stable releases, each release receiving updates for four years.
I do observe that 1) several major features were ready about 6 months after the 3.3 stable release that would have solved a real problem; and 2) I have code that is not ready for the 3.4 release, but I don't want to wait with until 2020. Both problems can be solved with a less-than-year release cycle. So that is what I plan to do. Wietse