This isn’t Lisa Preston’s site. It can be found here. However, I found the following answer to your question at http://www.agentquery.com which has a wonderful F.A.Q. on Submitting to Literary Agents http://www.agentquery.com/writer_sa.aspx ).

The answer to your question is is near the bottom so I’m going to include part of it here:

Is it okay to “simultaneously submit” to literary agents?

Simultaneously submitting to agents means you’re querying more than one agent at a time. And yes, you must simultaneously submit QUERIES, or you’ll never get anywhere. However, we do recommend that you pace yourself by sending queries out in batches. No more than ten or so. As you receive rejections and acceptances, you’ll also receive feedback, wanted or unwanted, warranted or not. You may find yourself revising your work, revising your query, or simply revising your search…Meter out your queries, and be sure to send your best work out into the world… don’t burn up all your options from the get-go by sending out forty queries in the first round. Instead, send out bunches of ten queries every two to three weeks.

I hope that’s helpful and thanks for joining us. I’ve got some new posts planned for April and am heading to the 2009 DFW Writer’s Conference in Dallas, Texas at the beginning of May. I’m certain to have a lot of information to report!