My answer is less than two months, depending on guidance and practice patterns.
Guidance really amounts to a wide array of talking about the tempo pattern, the feel of the tempo, the biomechanics of shoulder-torso action in relation to the hands, the tempo in short strokes and in long strokes, and what other movement patterns a good putting tempo feels like.
Practice amounts to a steady diet of the correct feelings of a good tempo in a variety of stroke sizes during the few weeks after first starting to engrain the nice-tempo stroke.
When I teach, the students often require a second lesson after about 1-2 weeks to get a solid grasp on how the tempo works with gravity and relaxation. There is a pretty deep-seated belief in practically all people that the ball has to be hit to make it move across the ground, and a smooth-tempo stroke that is indifferent to the ball and to hitting the ball is difficult to see as sufficient to roll the ball as far as required. So the faster the golfer-student watches and learns as the smooth stroke rolls the ball the correct distance, instead of clings to preconceived notions, the faster the golfer-student embraces the grace and consistency of the smooth stroke. Some are faster than others.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
Geoff Mangum's PuttingZone
Golf's most advanced and comprehensive putting instruction.
Over 950,000 visits and growing strong ...
518 Woodlawn Ave
Greensboro NC 27401
(336) 340-9079 cell
geoff@puttingzone.com
AIM: puttmagic
Yahoo!IM: puttmagic
MSN IM: geoff@puttingzone.com
ICQ#: 277025051