Can someone live with untreated brain mets with symptoms for 5 years or would they have been gone a long time ago?

One would most likely experience progressively worsening neurologic symptoms if they had cancer metastasis in the brain.

It would be uncommon, but never say never. You can reduce your risk of cancer by adopting healthy habits: Eat a mostly vegetarian diet, avoid alcohol, tobacco and street drugs, avoid excessive exposure to sun, maintain healthy weight, get HPV vaccine, exercise 30 minutes each day, drink enough water so your urine is mostly colorless. Wish you good health!