public function cleanOld()
    {
        $siteconfig = SiteConfig::current_site_config();
        $date = $siteconfig->dbobject("LastEstimateClean");
        $request = Injector::inst()->get(HTTPRequest::class);

        if (!$date || ($date && !$date->IsToday())) {
            $task = Injector::inst()->create(CleanExpiredEstimatesTask::class);
            $task->setSilent(true);
            $task->run($request);
            $siteconfig->LastEstimateClean = DBDatetime::now()->Value;
            $siteconfig->write();
        }
    }