Hi

The cjwnewsletter cronjob cjw_newsletter_mailqueue_process sends all emails in one go (in one execution).
line 81:

    // process every send_item of current sendobject
    for( $i = 0; $i < $itemsNotSend; $i += $limit)
    {
        .....

I havn't reproduced a case where this is actually a problem, but I assume there is a potential problem with this approach as you may hit the memory_limit etc.