How often should I submit my pages to the engines?

Question:
I recently purchased your book and am very pleased with the contents. However, I am unclear on a particular point which appears to be rather crucial - the actual submitting of pages. Several times references are made to resubmitting to search engines and in the statistics for each SE you give a figure for "database refresh." At first, I took this to mean that I needed to resubmit as often as a search engine refreshed its database. But now I'm not so sure. I was going through each search engine and cataloging which pages I needed to submit to which search engine and as I read each SE's "add URL" page I began to wonder whether I would be punished for resubmitting every couple of weeks. I then looked for an answer in the book only to become more confused. Before I do anything irreversible with the SE's could you please try to answer
this question for me: HOW OFTEN DO I NEED TO SUBMIT MY PAGE/PAGES TO EACH OF THE SEARCH
ENGINES?

Answer:
You only need to submit your pages when you have made a change and want the engines to pick up those changes. Most search engines slowly will revisit the pages in their index to see if they have been updated. Currently, there is little, if no benefit in resubmitting them when they haven't changed. Infoseek does give a VERY slight preference to new pages, but in most circumstances, it's not worth resubmitting daily and may even cause a penalty if you resubmit the same page real often.

The main reason we list the update times is so you have an idea how long it may be before the pages you have submitted will show up in the engine.

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