hi kc
the REST API session key has a validity of 30 minutes, as stated here: http://community.lithium.com/t5/Developer-Documentation/bd-p/dev-doc-portal?section=commv1&leaf-id=AuthenticationManager.sessions.login#AuthenticationManager.sessions.login
the post you linked is about Lithium Response, so not related to the Community.
There's no admin setting to change the timeout for the API session key, but you can reach out to support as I think there's a backend configuration for it.
In any case, your logic should be able to handle "session expired" errors and get a new session key in those cases.
Note: looks like config.mobile_session_timeout_minutes is an old setting that is not used anymore.
