At the moment, the portal that leads from serena tower to Sanctuary just leads back to Final Sanctuary if the character has access, making a guest pass to final sanctuary uncomfortably permanent. Its possible to find an exit through an illusion, but thats just about the only exit right now.
I'd love to use final sanctuary for more, but this puts a damper on passes a bit.
Sounds like a great way for the Spellguard to trap people.
"Why would you ever want to leave Final Sanctuary? Come, play with us, forever and ever and ever..."