Notice: This article may contain information for multiple versions of Passpack, be sure and read the section appropriate to your version. How do I know what version I'm using?
To see when they expire, go to Settings > Disposable Logins. If you have any active Disposable Login they will be listed there. At the top of the list, it should say something like "These Disposable Logins will expire in 11 hours and 59 minutes."
If you do not see a list, it means that they have already expired, therefore you have none.
Passpack v8 (Preview)