Change session expiration time dynamically - Code Igniter 3

How do I set a config.php configuration item before it was loaded? I need to change the $ config ['sess_expiration'] item, according to the user.

I tried the following: User.php

public function logar() {
    $login                 = addslashes(strtoupper($this->input->post("login")));
    $senha                 = addslashes(md5($this->input->post("senha")));
    $this->dados['login']  = $this->usuarios->getUser($login, $senha);
    $logged                = $this->dados['login'][0]->LOGGED;

    if (count($this->dados['login']) > 0) {

        if($this->dados['login'][0]->AUTORI == 1 || $this->dados['login'][0]->AUTORI == '1') {
            $this->session->set_flashdata('erro_login', 'Este usuário não está ativo no banco configurações!');
            redirect('');   
        }

        $sess[0] = (object) array(
            'idusua'      => $this->dados['login'][0]->IDUSUA,
            'nomusu'      => $this->dados['login'][0]->NOMUSU,
            'tokusu'      => $this->dados['login'][0]->TOKUSU,
            'sesexp'      => $this->dados['login'][0]->SESEXP,
            'logou_token' => false,
            'anomes'      => date('Ym'),
            'conusu'      => json_decode($this->dados['login'][0]->CONUSU),
            'condbu'      => array(
                'server' => $this->encryption->encrypt($this->dados['login'][0]->SERVER),
                'user'   => $this->encryption->encrypt($this->dados['login'][0]->USERRR),
                'pass'   => $this->encryption->encrypt($this->dados['login'][0]->SENHAA),
                'db'     => $this->encryption->encrypt($this->dados['login'][0]->DATBAS)
            )
        );

        $this->config->set_item('sess_expiration', $this->dados['login'][0]->SESEXP); // => nesta linha tentei setar, mas não sobrescreve o valor em config.php 
        $this->session->set_userdata("sessao", $sess);

        if($logged == 'N') {
            $this->usuarios->updateLogged($this->dados['login'][0]->IDUSUA, 'S'); 
            redirect('Principal/');   
        } else {
            $this->session->set_flashdata('erro_login', 'Usuário já está logado em outro dispositivo!');
            redirect('');
        }
    } else {
        $this->session->set_flashdata('erro_login', 'Dados informados inválidos!');
        redirect('');
    }
}

config.php

$config['sess_driver']              = 'database';
//$config['sess_driver']              = 'files';
$config['sess_cookie_name']         = 'ci_session';
$config['sess_expiration']          = 0; // se deixar 0, retorna 0 mesmo, se comentar a var toda, nao retorna nada porque nao existe
$config['sess_expire_on_close']     = TRUE;
$config['sess_regenerate_destroy']  = FALSE;
//$config['sess_save_path'] = APPPATH . 'ci_sessions/';
$config['sess_save_path']           = 'ci_session';
$config['sess_match_ip']            = TRUE;
$config['sess_time_to_update']      = 300;

Printing to debugg:

CI_Config Object (
[config] => Array
    (
        [app_version] => 1.0
        [base_url] => http://192.168.0.30/projetos/dashboard/
        [index_page] => 
        [uri_protocol] => AUTO
        [url_suffix] => 
        [language] => english
        [charset] => UTF-8
        [enable_hooks] => 
        [subclass_prefix] => MY_
        [composer_autoload] => 
        [permitted_uri_chars] => 'a-z 0-9~%.:&_\/-=?+',;()
        [enable_query_strings] => 
        [controller_trigger] => c
        [function_trigger] => m
        [directory_trigger] => d
        [allow_get_array] => 1
        [log_threshold] => 0
        [log_path] => 
        [log_file_extension] => 
        [log_file_permissions] => 420
        [log_date_format] => Y-m-d H:i:s
        [error_views_path] => 
        [cache_path] => 
        [cache_query_string] => 
        [encryption_key] => PuZDlRnAHX1qdjiBiFwegiVSTzK6XSln
        [sess_driver] => database
        [sess_cookie_name] => ci_session
        [sess_expiration] => 0
        [sess_expire_on_close] => 1
        [sess_regenerate_destroy] => 
        [sess_save_path] => ci_session
        [sess_match_ip] => 1
        [sess_time_to_update] => 300
        [cookie_prefix] => 
        [cookie_domain] => 
        [cookie_path] => /
        [cookie_secure] => 
        [cookie_httponly] => 
        [standardize_newlines] => 
        [global_xss_filtering] => 
        [csrf_protection] => 
        [csrf_token_name] => csrf_test_name
        [csrf_cookie_name] => csrf_cookie_name
        [csrf_expire] => 7200
        [csrf_regenerate] => 1
        [csrf_exclude_uris] => Array
            (
            )

        [compress_output] => 
        [time_reference] => local
        [rewrite_short_tags] => 
        [proxy_ips] => 
    )

    [is_loaded] => Array (
    )

    [_config_paths] => Array(
        [0] => C:\xampp\htdocs\projetos\dashboard\application\
    )

)