I think the question needs to be clarified a bit, it seems like some 'peeps' are confusing Top Speed on Flats versus Top Sprinting Speed which are TOTALLY not the same. A good sprint is usually about 500 meters give or take, whereas Top Speed on Flats, riding the American River Bike Trail for instance, which is mostly flat, can be as long as 10-15 miles.
Just my 2 cents