Python has followed an 18-month release cycle for many years now; each
new 3.x release comes at that frequency. It has worked well, overall,
but there is interest in having a shorter cycle, which would mean that new
features get into users’ hands more quickly. But changing that longstanding
cycle has implications in many different places, some of which have come up
as part of a discussion on switching to a cycle of a different length.

Source: LWN.net – [$] More frequent Python releases?