Control Panel Timeout Window
For security purposes, users are automatically logged out of the control panel if they are inactive for a specified amount of time. This amount of time can be configured to be up to two hours in your store's control panel Display Settings.
Actions such as creating/updating a product, navigating the control panel, and saving settings are all recognized as activity. Simply typing, in and of itself, is not considered activity, so if you're writing a long blog post or product description, be sure to save your progress every so often to prevent automatically being logged out (and potentially losing your work).
Five minutes prior to automatically logging you out, the control panel will pop up a warning and begin a countdown.