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.
If you are putting with The Frankly Frog putter it will help forgive your miss hits, which is especially useful on long putts.