Yes, it could take a couple hours depending on hardware and amount of content. Check for any other dialogs that might be behind the one that is not responding. There should be an additional dialog showing status progression through all the stages of the database upgrade. If you don't see that, you can also monitor the BESAdminDebugOut.txt file which will exist in %LOCALAPPDATA%\BigFix directory for the user running the upgrade. It will contain the message
Silent upgrade completed successfully! when the upgrade is done.