Tails has a time-based release schedule, aligned with Firefox ESR (Extended Support Release) that are put out every 6 weeeks:

• https://wiki.mozilla.org/Releases
• https://wiki.mozilla.org/RapidRelease/Calendar
• https://mail.mozilla.com/home/akeybl@mozilla.com/Release%20Management.html
• https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/

The rationale was originally written on tails-dev.

The idea is to put a major Tails release out every 12 weeks, plus a point release in between. See the calendar.

Schedule

  /          4w         \/   2w    /4d\

  previous               RC1    ESR sources
  ESR + Tails             |        |
  release          freeze |        |  new ESR + Tails
  |                     | |        |  release
  |                     | |        |  |
  ↓                     ↓ ↓        ↓  ↓
._____._____._____._____._____._____._____.
0     1     2     3     4     5     6

In the above:

• ESR sources means the source code for the upcoming Firefox ESR is available, but the ESR is not officially out yet: it has to go through Mozilla's QA process first. Sources are generally available on Friday night (US time).
• ESR + Tails release means Mozilla announces the new Firefox ESR, and we release a new version of Tails (roughly) the same day. This usually happens on Tuesday night (US time).

What if things go wrong?

Postponing the final release causes problems for those who have scheduled time for post-release user support, press work, etc..

Also, changing our mind (i.e. releasing a point-release instead of a major one) => switching minor/major release schedule for the future is probably not an option either.

So we need to have a pessimistic enough RC->final schedule to handle unexpected issues.

Reverting the faulty feature branch is an option too.

Some day, a freezable APT repository will remove quite some of the potential for last minute breakage.

Remaining issues

• When to run the test suite: RC1 and/or RC2?