another helpful thing that I do when using drush for civi upgrades:
since drush does not give you any information about where in the process the upgrade is (the GUI has the progress bar that says what version it is at) I open another ssh session to the server and use drush civicrm-sql-clidrush civicrm-sql-cli
to get into the sql console with the right database. Then as the upgrade runs in one terminal I repeatedly run the following query to follow the progress -- especially in upgrades that span multiple versions --
select version from civicrm_domain;:
select version from civicrm_domain;