Session express when I use ajax imap

Hello,

I use ajax to call some imap functions how ever the session tends to expire before the sess_expiration 7200 limit.

I am not sure if it is some thing to do with session_time_to_update?

Any suggestions what I should change?

PHP Code:

$config['sess_driver'] = 'files';
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = BASEPATH . 'cache/admin/session/';
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = TRUE;