Valerie Strauss's blog The Answer Sheet has a wonderful post on the limitations of time constraints. Props to Valerie as she is a writer who truly gets education.
Few tasks in life--and very few tasks in scholarship--actually depend on being able to read passages or solve math problems rapidly....IIndeed, by eliminating the timed component, the College Board would signal that background knowledge, seriousness of purpose, and effort--not speed and glibness--are the essentials of good scholarship. And if, in the future, students were allowed to bring dictionaries, or even to have access to the Web, so much the better. Such a change would far more accurately duplicate the conditions under which serious individuals at any level of expertise actually do their work.