Do I have to have surgery for an anal prolapse that won’t come back for years?

Not necessarily.
If an anal prolapse does not return for many years, you should seek prompt medical attention to improve the relevant tests and make a clear diagnosis. The specific treatment should be decided by taking into account your age, your own condition and the tests. In children, for example, rectal prolapse is a self-limiting condition that can heal spontaneously by the age of five and is treated primarily with non-surgical treatment.