That's False. You should change them now if you can. Save some money and do it yourself. Its pretty easy. You should have the transmission fluid changed as well.
That is absolutely not true for gearboxes. Even for transmission, I certainly wouldn't worry about it at 122K. Plenty of threads on how to do it on the forum. Only need a few tools you might not otherwise have like 24mm socket and 10mm hex socket.
You can easily knock out both differentials and transfer case in under two hours.