If you want to see how a web page performs for a frequent visitor, or someone who already has elements from the page cached, you can turn on the return visitor flag on the task edit screen.
Simulate a Return Visitor immediately revisits the web page a second time and only records the results of the second visit. Results may differ from a first visit (which always starts with an empty cache) based upon how the browser handles certain items, such as the expiry of elements on the page.