Once your vision has returned to normal more permanently, it becomes easier to keep it so. Seeing blurry involves a lot of strain that is taxing on your energy. Seeing clearly is a habit of correct use of your eyes that you (re)learn and is inherently easier and more preferable as you get used to it. The exercises only help you on your way. If you do find your vision slipping at some point, you know what to do to re-establish the clear vision, whether it's temporary use of some exercises or just a moment of examining how you're using your eyes and re-asserting the correct way that you have already learned. People with normal vision do not do exercises to maintain it, and neither do you need to. Your eyes are used all day long, and the way they are used all day has a much bigger impact than anything else. Similar to how your heart is challenged and becomes healthier by intense physical activity, your eyes are challenged by difficult visual situations and become better able to adapt to them.
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"I conceive that the great part of the miseries of mankind are brought upon them by false estimates they have made of the value of things." - Benjamin Franklin