My 2ยข would be ...
... is that when the tobacco is grown, or I should say what time it is ready for harvest, has nothing to do with it ... since the leaves have to be aged first before they are rolled. It is a somewhat complex process that sometimes can take 3 to 5 years, if not longer, depending on how those leaves are going to be used in the building of the cigar.
It's all in the timing, and bringing all of these different variables together ...
My best answer to your question, is that there are no set times when various cigars are ready for release. The biggest factor would be, is when the person who is in charge of their release feels that they have met the criteria and standards set for them.
There are exceptions that we all know about, for example, the seasonal cigars that come out around the holidays (such as Fuente's BTL, Work of Art, etc.) ... but these speciality lines have been carefully planned for years for release at that predetermined time.
Other factories may have similar ones they release at certain times of the year also, but I am more familiar with the Fuente lines ...