Till know, i didn't find anyone said that sunken eyes will be permanent. And those sunken eyes can be treated by some ways. As far as i know, there are some home remedy to help you treat sunken eyes.
1. You should do everything you can do to improve your sleeping. Lack of sleep or bad sleep can be one of the factor of sunken eyes. So, get good sleep can help you prevent the occurrence of dark circles.
2. You can considered to use hot compress. Apply warm teabag on your eyes that help improve the circulation of blood around the eyes.
3. Use some scream that used for dark circles that also helps.
Some people getting the sunken eyes are born to be. While others get this because of the environment effect, such as wearing the high prescription eyeglasses, stay up too late and so on. However, the sunken eyes have much relationship with orbital fat in the eyes. It is hard to get rid of since you get it unless you take the surgery which may thoroughly help you get rid of this. And after the surgery, you may get the basic recovery after a week. Then you should take care of your eyes, not smoking, drinking and eating the spicy food.
Well, it is kind of difficult to tell how long the sunken eyes can be. Generally speaking, sunken eye can disappear in several days. But on the other hand, there are also some people who always haven sunken eyes, for sunken eyes can be hereditary. So it all depends on the situation you have. But you can try some ways to reduce the symptom. For example, you can some moisture, like L'Oreal Active Daily Moisture Lotion. You can just put them on your whole face, and especially under my eyes. For a long time, it will tighten the skin and make it glow in a healthy way. And also, you can just have a good rest and drink enough water and eat fruits, so it can be good for your sunken eyes.