After about two to four weeks of practice you may think that no improvement is experiencing, that you can not hold the alphaphase for long time. But if you walk through a familiar environment, you will soon realize, that your vision has improved enormously, even in the beta phase. You may now read street signs and house signs, which you could not decipher without glasses for years. So, do not be demotivated, if you can hold the alpha phase only for a short time. With each exercise you will improve your ability to see your environment more sharply.
Your eyesight seems to improve apparently slowly. But in reality there is a progress with every exercise you make. And this progress is clearly visible also in the beta phase.