Thanks for the reply.

I consider mail client as a program which runs in the background. I am 
not engaged in it actively all the time, but respond to alerts. Since 
situations of being away from the desk/office happens quite 
intermittently in a typical day, paying attention to closing the 
application every time (or paying attention to when the AFS token are 
likely to expire) seems like unnecessary user involvement on something 
which computers are otherwise very good at handling.

-aki