docs: Add new summary section to the release lifecycle page.

docs/overview/release-lifecycle.md

@@ -1,8 +1,25 @@
 # Release lifecycle
 
-This page documents how the various components of Zulip released are
-managed as well as our backwards-compatibility and security support
-policies.
+This page details the release lifecycle for the Zulip server and
+client-apps, well as our policies around backwards-compatibility and
+security support policies. In short:
+
+* We recommend always running the latest releases of the Zulip clients
+  and servers. Server upgrades are designed to Just Work; mobile and
+  desktop client apps update automatically.
+* The server and client apps are backwards and forwards compatible
+  across a wide range of versions. So while it's important to upgrade
+  the server to get security updates, bug fixes, and new features, the
+  mobile and desktop apps will continue working for at least 18 months
+  if you don't do so.
+* New server releases are announced via the low-traffic
+  [zulip-announce email
+  list](https://groups.google.com/forum/#!forum/zulip-announce). We
+  highly recommend subscribing so that you are notified about new
+  security releases.
+* Zulip Cloud runs the branch that will become the next major
+  server/webapp release, so it is always "newer" than the latest
+  stable release.
 
 ## Server and webapp
 
@@ -22,7 +39,10 @@ server repository][zulip-server].
   fixes, and improvements to Zulip's internals.
 * New maintenance releases, like 4.3, are published roughly once a
   month. Maintenance releases are designed to have no risky changes
-  and be easy to reverse, to minimize stress for administrators.
+  and be easy to reverse, to minimize stress for administrators. When
+  upgrading to a new major release series, We recommend always
+  upgrading to the latest maintenance release in that series, so that
+  you use the latest version of the upgrade code.
 
 Starting with Zulip 4.0, the Zulip webapp displays the current server
 version in the gear menu.  With older releases, the server version is
@@ -55,7 +75,8 @@ in a stable release.
   release.  Self hosters can [upgrade][upgrade-from-git] to these
   stable release branches to get bug fixes staged for the next stable
   release (which is very useful when you reported a bug whose fix we
-  choose to backport).
+  choose to backport). We support these branches as though they were a
+  stable release.
 * Self-hosters who want new features not yet present in a major
   release can [upgrade to master][upgrading-to-master] or run [a fork
   of Zulip][fork-zulip].
@@ -183,9 +204,10 @@ of our [upgrade nag](#upgrade-nag).
   connected to organizations hosted by different servers).
 
   The desktop apps automatically update soon after each new
-  release. Because Zulip's desktops apps are implemented in Electron
+  release. Because Zulip's desktop apps are implemented in Electron
   and thus contain a Chromium browser, security-conscious users should
-  not disable automatic updates.
+  leave automatic updates enabled or otherwise arrange to promptly
+  upgrade all users after a new security release.
 
   New desktop app releases rarely contain new features, because the
   desktop app tab inherits its features from the Zulip server/webapp.

docs/production/install.md

@@ -106,11 +106,13 @@ together with using it with you.
 
 Learning more:
 
-* Subscribe to the
-[Zulip announcements email list](https://groups.google.com/forum/#!forum/zulip-announce)
-for server administrators.  This extremely low-traffic list is for
-important announcements, including new releases and security issues. You can also use the
-[RSS feed](https://groups.google.com/forum/#!aboutgroup/zulip-announce).
+* Subscribe to the [Zulip announcements email
+list](https://groups.google.com/forum/#!forum/zulip-announce) for
+server administrators.  This extremely low-traffic list is for
+important announcements, including [new
+releases](../overview/release-lifecycle.md) and security issues. You
+can also use the [RSS
+feed](https://groups.google.com/forum/#!aboutgroup/zulip-announce).
 * Follow [Zulip on Twitter](https://twitter.com/zulip).
 * Learn how to [configure your Zulip server settings](settings.md).
 * Learn about [Backups, export and import](../production/export-and-import.md)