04-sessions.md in stealth-1.1.0.rc1

- old
+ new
@@ -13,5 +13,17 @@
 User sessions are stored in Redis. Each session is a lightweight key-value pair. The key is the user's ID from the service -- so for Facebook it may be a long integer value: `100023838288224423`. The value is the flow and state for the user separated by a "stabby" operator (`->`).
 
 So if for example a user with ID `100023838288224423` is currently at the `hello` flow and `ask_name` state, the value for the key would be: `hello->ask_name`.
 
 You likely won't be interacting with sessions directly since Stealth manages it automatically for you. We just present it here for clarity into how sessions work.
+
+## Session Expiration
+
+By default, Stealth will not expire your user sessions. If you want your sessions to expire, you can set the `session_ttl` option:
+
+```ruby
+Stealth.config.session_ttl = 2_592_000 # seconds (30 * 24 * 60 * 60)
+```
+
+The above configuration setting will result in stale keys expiring in 30 days. Sessions that have been accessed reset the TTL (time to live). If you set a value of zero (the default), session expiration will be disabled.
+
+If a user returns to your bot after their session has expired, they will start again in the `Hello` flow or whatever you have defined to be your first flow.