Question about Cookie expiration

[eluser]Kraig[/eluser]
In the config file I changed config['sess_expiration'] to be equal to 10 seconds...testing purposes.

Now in my code after the user has logged in I try and reset the sess_expiration by use of the following code:

Code:

$this->session->set_userdata($data);
    $this->config->set_item('sess_expiration', 7200);
    redirect('home/home');

How come the user is still being logged out after 10 seconds? Did I not change it to 7200??