On one of the law school websites (can't remember which one though) they said to submit it for the first 10, wait until it is complete, sent to the law schools, and you get the SAR. Then you need to edit and resubmit it to send to the other law schools. It takes a few weeks.
If you change the schools and resubmit before the results have been sent to the first set of schools, they might never get the information.
Make sure to keep deadlines in mind when you're choosing which ones to submit FAFSA for first.