If you follow the link I provided, there is some discussion on using ini_set to over ride the servers settings at run time. In some cases, this can work, in other cases not.
At the end of the day, this is a server configuration issue, the people that will be able to help you are your host. they may have advice on setting up an htaccess file that can extend the session time out, or they may be able to edit the INI file for you. If the session time out settings _can_ be altered on your server, the host will be able to offer you advice on how to accomplish it.
