How many years can you go without having ptosis surgery again?

Ptosis: Ptosis usually refers to drooping or sagging of tissue or a particular structure, and is not a diagnosis in itself. However, I am assuming you are talking about your eyelids, in which case, would probably depend on when it restricts your visual field of view. Most issues involving Ptosis of a structure are going to be more quality of life issues, and the individual is the one who determines when.