The default timeout value for the vCAC web console is 30 minutes. You might find this not long enough or too long, whatever your reasons are, if you want to change it you can.
Access the vCAC Appliance through SSH (with Putty for example) or access the virtual appliance console directly to modify this file:
for 6.0 /usr/lib/vcac/server/webapps/shell-ui-app/WEB-INF/web.xml
for 6.2 /usr/lib/vcac/server/webapps/vcac/WEB-INF/web.xml