Most golfers, I have seem approach every putt with a methodical "pendulum" shoulder motion,  this may surprise you to find that on putts more than 20 feet it does not matter if you putt wit a pendulum method, you may still miss the hole.  To get the maximum distance you can out of your putt, try incorporating a slight bowl in your wrist(wrist cock) into your backswing. With a long lengthly putt the pendulum stroke runs the risk of twisting the club face offline, with a slight wrist cock putter face remains on track with your putting line.  A tip, keep this wrist cock stroke short at first, so you can gage the distance.  Practice this stroke on the practice green before your round, get the feel of distance control.  


Enjoy your next round of golf.