So you like it at the top! It can take up to 6 months for the search engines to fully list your site. In that time, you can have pages dropped off their databases, and you need to be sure that you keep your position. That is why every month, we check to see if you are listed, and if not, we resubmit your page. Some of this is automated, but some is manual as Google for one do not like automated queries.