public function mustRefresh()
    {
        if ($this->fileExists()) {
            $this->_cleanFilesStack();
            $_dest = new \SplFileInfo($this->getDestinationRealPath());
            if (!empty($this->files_stack)) {
                foreach ($this->files_stack as $_file) {
                    if ($_file->getMTime() > $_dest->getMTime()) {
                        return true;
                    }
                }
                return false;
            }
        }
        return true;
    }