The amount of reverse makes little or no difference in normal landing conditions to the stopping distance. This is decided by the autobrake (or foot pressure on the brakes) which will give a predetermined decelaration. In most cases all reverse does is help reduce brake wear and make the flight crew feel they are being proactive in helping stop the aircraft.
Some crews may elect to use more than reverse idle to help keep brake temps down on short turnarounds, especially if the aircraft has no brake fans.