Does mono ever fully go away ?

Yes, give it time: The acute symptoms of infectious mononucleosis (mono), such as fever, sore throat, and enlarged lymph nodes, typically last 2-3 weeks. Fatigue may last longer, but most people feel entirely well after 1-2 months. Once in a while, tiredness etc may last 6 months. But eventually it clears up entirely. Follow up with your doctor if you have continuing symptoms or otherwise remain concerned.

Define "go away" ?: The clinical illness certainly fades over time in people. Years ago there was some idea that chronic fatigue was related to mono but the CDC reviewed the data and found that to be discredited. The germ involved is from a family of viruses that can hibernate in your system forever. So you can get over the illness but retain the germ in your system.You might also shed the germ intermittently.