We use a hands on approach and , browse the directories about once a omonth and from the thumbnail picks constantly updated by msn you can get rid of dead links and also the ones that are moved to parked domains, duplicate content sites/etc.
NOTICE: I will be updating the biz-giant directory to phpld platform as well as going threw Sleek and Biz-King shortly and removing sites that are parked as well as sites that have no value and were collected when the directories were New and FREE This does not mean that if your site was FREE submittion will it be removed BUT stating that irrelevant sites in irrelevant categories as well as poorly designed sites or those that NOW have adsence threw out will deleted and Notices sent to perspective submitters... thx malcolm1