Session live timeout when 2 hour

I’m using PHP Version 5.2.13, session.save_path = no value and wordpress 4.2.2.

I have a problem when i has login with function wp_signon.

    $creds                  = array();
    $creds['user_login']    = $_POST['txtLoginID'];
    $creds['user_password'] = $_POST['txtLoginPassword'];
    $creds['remember']      = true;
    $user                   = wp_signon( $creds, false );       

But after 2 hour, my account have been logged out.
How to keep login in 2 week. Thank you so much!