public function getDuration()
    {
        $duration = false;
        if ($this->getExecutedAt() && ($this->getExecutedAt() != '0000-00-00 00:00:00')) {
            if ($this->getFinishedAt() && ($this->getFinishedAt() != '0000-00-00 00:00:00')) {
                $time = strtotime($this->getFinishedAt());
            } elseif ($this->getStatus() == Aoe_Scheduler_Model_Schedule::STATUS_RUNNING) {
                $time = time();
            } else {
                // Mage::throwException('No finish time found, but the job is not running');
                return false;
            }
            $duration = $time - strtotime($this->getExecutedAt());
        }
        return $duration;
    }