The actual malice standard applies only to subject matter related to the controversy in question or to the field in which the individual is prominent, not to the person's entire life.
Passage of time does not affect an individual who has achieved fame through participation in a controversy as long as the public maintains an "independent" interest in the underlying controversy.
See this Chart of Public vs Private Individuals for additional examples.
Defining who is a public figure for purposes of First Amendment protections is a question of federal constitutional law, and therefore the federal courts say on the matter is decisive and binding on state courts. Accordingly, state courts cannot remove public-figure status from those who have been deemed public figures by the federal courts, but states can broaden the scope of the the classification. For example, while the Supreme Court has not spoken on the status of educators, most states have recognized teachers as a class of public figures. But some states, for example California, have not done so. Consult your State Law: Defamation section for specific guidelines on your jurisdiction.
Negligence Standard and Private Figures
Those who are not classified as public figures are considered private figures. To support a claim for defamation, in most states a private figure need only show negligence by the publisher, a much lower standard than "actual malice." Some states, however, impose a higher standard on private figures, especially if the statement concerns a matter of public importance. You should review your state's specific law in the State Law: Defamation section of this guide for more information.