For the right handed golfer a big 90 degree shoulder turn allows the arms to travel a full distance and get a lot of width and then on the down swing turn the hips through and really power into the ball. So a big 90 degree shoulder turn on the way back is a sure fire way of increasing the distance.
Right Hand Golf Tip: Aim your Body Right to Help Increase your Backswing Turn (Video) - by Peter Finch