There is no such thing as a predetermined or mandated expiration date on fall protection harnesses. Neither OSHA nor ANSI have current codes or standards that set a specific time period for taking a harness out of service. Even most manufacturers will not suggest how long a harness will last.
In fact, the only person who can truly determine when a harness is due for removal is you or your competent, trained inspector. More important than who determines its end of life is what determines it.
Ultimately, the decision to retire a safety harness is up to you, once you’ve clearly evaluated the effectiveness of the harness. As long as it passes your user inspection both daily for pre-use and annually by your competent person you are okay to use these products all the time.