The concept of "Mean Survival Times" could be understood as the average life span or duration of survival. The antonyms for this term could vary depending on the context in which we use it. For instance, if we think of life expectancy, the antonyms could be words such as "immortal," "eternal," or "indestructible." On the other hand, if we take into account the survival of certain species of animals or plants, antonyms such as "endangered," "vulnerable," or "extinct" could be used. Similarly, if we talk about a patient's condition with a terminal illness, antonyms such as "recovery," "rejuvenation," or "cure" could be considered.