I made two minor changes to the Twitter StreamGraphs application. First of all, you now get the latest 1000 tweets containing your search term rather than the latest 200. Secondly, I changed the default search term to 'data visualization'. The first change should help make it a little more useful although for any popular term 1000 tweets doesn't go back very far.
One technique that might be useful is to include more simple words in the query that will match fewer tweets and let you see back farther into time. For example a search on 'coffee' will likely only show a couple of hours back but a search on 'coffee to the and' goes back almost two days. If you are using the 'q=' parameter in the URL then separate different words with '+' like so: http://www.neoformix.com/Projects/TwitterStreamGraphs/view.php?q=coffee+to+the+and
Twitter StreamGraph for 'Data Visualization' (click to use interactive tool)