Who not a guaranteed minimum of 25 years after publication (for posthumous works and authors who kick the bucket shortly after publication) with the expectation

Who not a guaranteed minimum of 25 years after publication (for posthumous works and authors who kick the bucket shortly after publication) with the expectation of lifetime of the author should they live more than 25 years after publication? The heirs of the long-lived authors will have to take the personal responsibility to have their own creative ideas instead of trading on their father's legacy.