1. Putty into vCenter Appliance as root.
2. Type the two commands shown below to access the regular shell.
3. Change directories to /etc/vmware/vsphere-client. It used to be in the /var directory in previous versions.
4. Edit the webclient.properties file and change the parameter session.timeout to 0 if you want to
make sure the web client session never times out. The default is 120 minutes. Use the vi editor to make that change. Then verify with the grep command.
5. Restart the web client service with the command /etc/init.d/vsphere-client restart
Note: For the Windows version, here is the information...