'Twitter Setup' option 'Delete old statuses' select box doesn't refresh

I noticed that after going to administer -> twitter setup and configuring the 'delete after' option, returning to this page always showed "Never" as the selected option. This happened several times after resaving the option.

Checking around, the related variable is 'twitter_expire', which is set in file 'twitter.pages.inc'. It looked like the DB table had the correct value, so I believe the problem is in line 27 where it's looking for the value of 'amazon_refresh_schedule' which doesn't exist. Changing that to 'twitter_expire' seems to fix the issue. I'm listing this as 'minor' because the DB has the correct option, but just doesn't display it on the admin page.

  $periods = array(0 => t('Never'));
  $periods += drupal_map_assoc(array(604800, 2419200, 7257600, 31449600), 'format_interval');
  $form['import']['twitter_expire'] = array(
    '#type' => 'select',
    '#title' => t('Delete old statuses'),
    '#default_value' => variable_get('twitter_expire', 0), // !!! originally 'amazon_refresh_schedule'
    '#options' => $periods