This forum is full of SAS Navy Seals and virologists, not orthopeadic experts! 🫣🙃🤭
They try their best to only do a TKR once per leg, because a second one (when the first wears out) is very hard to do. So, if you're fit at 69, @retarius has the better answer for you. TKR's rarely last more than 20 or so years and it sounds like you might have more than that left in your tank.
Good luck!