I'm not familiar with GL1.3, but you could try just remove the overriding line of code (the badly commented one that should read "can", not "can't" )
Text Formatted Code
$_CONF['cookie_ip'] = 0;
$_CONF['default_perm_cookie_timeout'] = 28800;
$_CONF['default_perm_cookie_timeout'] = 0; //jcg 4/12/2011 so users can't stay logged in forever
$_CONF['session_cookie_timeout'] = 7200;
$_CONF['cookie_path'] = '/';
$_CONF['cookiedomain'] = ''; // e.g. '.example.com'
$_CONF['cookiesecure'] = 0;
Text Formatted Code
$_CONF['cookie_ip'] = 0;
$_CONF['default_perm_cookie_timeout'] = 28800;
$_CONF['session_cookie_timeout'] = 7200;
$_CONF['cookie_path'] = '/';
$_CONF['cookiedomain'] = ''; // e.g. '.example.com'
$_CONF['cookiesecure'] = 0;
That's for 8 hours.