Clicking on check for updates, only forces the client to check the Tablo for anything new.
The Tablo will check the Tablo Servers every 4 hours or during reboot.
For example, you are watching the Tablo through a Roku. While you are binging Judge Judy, the Tablo calls home and finds an update available.
Your show will not be interrupted, you will not know an update is available, until. you either disconnect and reconnect the client or you click the check for updates button.