You may want to initiate the cPanel update process in SSH to run in the background even if you exit the terminal.
The upcp script at
/usr/local/cpanel/scripts/upcp has a
--bg flag for running the upgrade in the background. If you want to force cPanel to update to the latest version on the currently configured upgrade tier, you can run the following command as root:
/usr/local/cpanel/scripts/upcp --force --bg