The session timeout parameter can be changed in WLAN > Edit. By default the session timeout parameter is configured for 1800 seconds before a reauthentication happens.
It is possible to change this value to anything, for example, it can be set to 180 seconds in order to make the client reauthenticate after three minutes.
Note: Sometimes a change in the session-timeout does not take effect. If this happens, try to upgrade the controller.
Also, check to see if the RADIUS Server (ACS) is configured for the same timeout value. The RADIUS attribute 27 is used in order to configure the session-timeout values.
In order to set this, choose user/group setup > Edit Settings > Radius[5842\001], and type the session timeout value in the Cisco-Aironet-Session-Timeout box. If this attribute is not listed under user/group setup, choose Interface config > Radius (IETF), and check the attribute  Session-Timeout for user/group.