One thing I see all too often on the lesson tee is a player whom makes a great swing to the top only to lose it at the very end when they forget to maintain the width of the arms at the top. In fact, this simple thing can cause you to hit the ball all over the course, not to mention, shorter. Whenever your arms go soft at the top- where your forward arm breaks down- you will narrow the swing arc thus the club does not stay in the air as long as it should.
The longer the club stays in the air on the backswing the more time you have create more speed and the arms play a huge role in this overall. In order maintain arm width to the top the focus should be to keep the hands as far away from the head as possible at the top. This action lengthens the rear arm to the top and extra width will be created. The more of this width you have the longer you will hit the ball in the end!