I'm not sure I understand the auto-update process in terms of when Adobe Flash is in use. I ask because when my computer is on Flash is always being used, be it streaming or videos.
I've not yet been updated to version 11.4.
In one of the last major versions (I think 11.2) we changed the way we named our plugin so that we could always update to a new version, regardless if the current one was in use. However, after updating, this does mean you need to either open a new browser tab, restart your browser, or in the case of the current version of Firefox (which has a bug that Mozilla will be addressing) possibly restart your system.
For details on how the update system works, please see this FAQ: How does the automatic update feature in Flash Player 11.2 work on Windows?