The GUI times out after 60 seconds.
Since the the "exec-timeout" setting has a default of 10 minutes (if I'm not mistaken), I don't think I could change the timeout value with that command.
Under the "Association" tab of the GUI, there is an "Activity Timeout" subtab and settings for 5 device classes, all set at 60 seconds.
I would guess the setting in question can be configured here.
Is the client station device class what I'm after?