public function prolong($key, $secs)
    {
        $item = $this->set($key);

        $expiration = $item->getExpiration()->getTimestamp();

        $now = time();

        if ($expiration > $now) {
            $interval = ($expiration - $now) + $secs;
        } else {
            $interval = $secs;
        }

        $item->expiresAfter($interval);

        $this->adapter->save($item);

        return $item;
    }