From a purely mathematical point of view, the best age would be in your early 20’s. The younger the egg cells are, the better the quality and accordingly, the higher the probability that you will achieve a successful pregnancy with the frozen egg cells. With every year you wait, the quality of the egg cells decreases and thus, the probability of a successful pregnancy. But most women only realize later how their life plans develop. In addition, if you plan to become pregnant before 30, you do not need to undergo unnecessary treatment. The optimal period is therefore between the late 20s and early 30s, but definitely before 35 years of age, as the number and quality of egg cells afterwards drop significantly. Of course, it is also possible to freeze your egg cells after 35 years. The challenge is that there are usually fewer egg cells available, but at the same time more egg cells are required in order to achieve a sufficient probability of becoming pregnant.