diff --git a/Civi/Api4/Action/ContactCategory/Sync.php b/Civi/Api4/Action/ContactCategory/Sync.php
index a7dde97..77bcd01 100644
--- a/Civi/Api4/Action/ContactCategory/Sync.php
+++ b/Civi/Api4/Action/ContactCategory/Sync.php
@@ -17,18 +17,27 @@ use CRM_Core_DAO;
  */
 class Sync extends \Civi\Api4\Generic\AbstractAction {
 
+  /**
+   * Usually this will not act unless the time is right.
+   *
+   * @default FALSE
+   * @var bool
+   */
+  protected $force = FALSE;
+
   public function _run(Result $result) {
     ini_set('memory_limit', '256M');
     Civi::log()->debug('Begin', ['=start' => 'ContactCatSync', '=timed' => 1]);
-    $settings = Civi::settings()->get('contact_categories');
+    // this does not unserialize $settings = Civi::settings()->get('contact_categories');
     $settings = Setting::get(FALSE)
       ->addSelect('contact_categories')
       ->execute()->first()['value'] ?? NULL;
     if (empty($settings['groupIDs'])) {
       throw new \API_Exception('Unconfigured');
     }
-    if ($settings['updateAfter'] > time()) {
+    if (!$this->force && time() < $settings['updateAfter']) {
       // not needed yet.
+      Civi::log()->debug("Skipping because not due until " . date('H:i j M Y', $settings['updateAfter']), ['=' => 'pop']);
       return;
     }
 
@@ -49,7 +58,7 @@ class Sync extends \Civi\Api4\Generic\AbstractAction {
       }
     }
     if ($smartGroups) {
-      Civi::log()->debug('Refreshing smart groups', ['=' => 'timed', 'groups' => $smartGroups]);
+      Civi::log()->debug('Refreshing smart groups', ['=' => 'timed,start', 'groups' => $smartGroups]);
       \CRM_Contact_BAO_GroupContactCache::loadAll($smartGroups);
       Civi::log()->debug('', ['=' => 'pop']);
     }
@@ -150,8 +159,16 @@ class Sync extends \Civi\Api4\Generic\AbstractAction {
     $summary['changes'] = $n;
     $_ = memory_get_peak_usage(TRUE);
     $summary['memory_use'] = @round($_ / pow(1024, ($i = floor(log($_, 1024)))), 2) . ' ' . ['b', 'kb', 'mb', 'gb', 'tb', 'pb'][$i];
-    Civi::log()->debug('Complete.', ['=' => 'set']);
     $result->exchangeArray($summary);
+
+    // Limit to running every 6 hours.
+    $settings['updateAfter'] = time() + 60 * 60 * 6;
+    Setting::set(FALSE)
+      ->addValue('contact_categories', $settings)
+      ->execute();
+
+    Civi::log()->debug("Complete. Scheduling next run after " . date('H:i j M Y', $settings['updateAfter']), ['=' => 'set']);
+
   }
 
 }