If you hit the center of the green the odds are that you will not have a putt longer than 30ft. If you are going to practice long putts, practice 30 footers.
Distance control is very important. To improve your distance control maintain good rhythm on your stroke. Don’t be scared to take the putter back far enough, keep your eyes on the ball and make a naturally rhythmic stroke. Avoid trying to hit the ball hard.
Allow your intuitive ability to dictate how far back you take the putter, the same as throwing a ball to someone.
The Frankly Frog putter will forgive your miss hits, which is especially useful on long putts. The Frankly Frog is the putter design now emulated by mallets used on the tour, but never equaled.