Force ICA listener settings on reconnected session - XenApp 4.5

I have a farm of XenApp 4.5 servers running on Win2003 R2.  Each server has two NIC’s – one on the production LAN for connections from our office locations, and one in the DMZ for connections from the internet.  An ICA listener is bound to each NIC.  

I have to set the disconnect timeout for the external connection to 15 minutes due to compliance reasons.  Internal LAN connections have a 24 hour disconnect timeout.  Sessions for both listeners are set to disconnect on timeout or a broken connection.

The issue I am running into is that ICA sessions appear to hold onto timeout settings from the listener they *first* connected to.  So, if a user works all day from the office, disconnects their XenApp sessions, and then reconnects from home through the internet, they have the 24 hour disconnect - even though they connected to the DMZ NIC/ICA listener.  This is a compliance violation for us.  

It works the other way around as well.  If a user checks their email from home first thing in the morning, disconnects, and then reconnects from the office, they will be bugged with the timeout warning every 15 minutes.

Is there a way to force the listener settings on a reconnected session?  I would prefer to not have to force a 15 minute timeout for internal LAN connections, or have sessions logoff on disconnect.

Thank you!