Contrary to popular opinion, submitting a website every week or every month to the major search engines will not help your rankings, in fact it might do just the opposite. Once a website is in a search engine's database, it usually won't go away with time. For all intents and purposes, once a website has been professionally optimized for all its major keywords & key phrases, normally the site should consistently yield excellent, positive results and will drive targeted visitors into your business. You should be careful of any company or individual that claims otherwise.
It isn't necessary at all to resubmit a website every month, but even if it was, there are simply not "thousands" of search engines that are worth submitting to! In the real world, there are only about a dozen or so major Web search engines and a few good search directories that, as a whole, provide about 96.5% of all Internet search engine results in the world.
Many businesses and large companies are flooded daily with useless spam and emails that claim to offer a monthly submittal service for a small fee. The majority of the search engines that these services plan to submit your site are, for the most part, totally unknown to the search engine community.
So what do you get in return for paying the monthly charges? Well less money in your bank account, plus knowing that your site will NOT be visible by the important search engines such as Google, Yahoo, DMOZ, Alta-Vista, etc. We have even heard things that Google may sometimes actually downgrade a site when resubmitted every week. It all depends on how serious your marketing program is.