How long is the good engine certified to operate when exposed to level X vibration? What level are they tested to, especially for 90+ minutes.
You seem to be talking about one single running engine's vibration. That concern is that it may lead to some accessory tubing break and the need to shutdown that engine.
This thread is about an engine already shutdown for cause (fan rotor wobble) and it's vibration level is at a very low frequency not likely to cause the loss of another critical system including another engine position (lots of damping through all the joints between isolated systems)