Only your second sentence is true. Once it overheats then yes, you’ll likely need to replace the unit.Frequent oil changes in the PTU doesn't stop it from overheating, though. Once it overheats, fresh oil or not, it overheated.
However, frequent oil changes absolutely stops it from overheating in the first place. That’s the whole point why so many on the forum recommend ptu oil changes every 20-30,000 miles. New oil provides more protection and is less likely to break down into a sludge over a short amount of time.
It’s also really simple and cheap to change especially in model years with the drain plug.