Express is not limited to 30 days, but it has to be able to contact Delphix at least once a week or it goes into lockdown mode, meaning you can still use it but can't create new objects.
If you go to the Express URL/ServerSetup.html and login as sysadmin, you should be able to click on "Support Bundle" menu at the top, and then choose upload support bundle. This should reset the appliance to clear the lockdown mode.
- Kyle