In our primary gateway, I sometimes see many unauthenticated perspective sessions that seemingly never close, so I terminate them.
We have another test gateway with the same settings, when I log out of a perspective session, the entry in the perspective session list turns Unauthenticated and then closes after 30 seconds or so.
I can't seem to find a setting that controls this anywhere. I checked the IdP session activity timeout and that's set to 30 minutes on both. What else controls this?