public function isExpired()
    {
        if (is_object($this->ExpireAtDate)) {
            $this->ExpireAtDate = $this->ExpireAtDate->Value;
        }

        $expired = false;

        if (!empty($this->ExpireAtDate)) {
            if (SS_Datetime::now()->Value >= $this->ExpireAtDate) {
                $expired = true;
            }
        }

        return $expired;
    }