Even though a benign brain tumor is not the cancerous type of brain tumor that would kill you if it were cancerous the brain tumor even when it's benign can kill you eventually if it's not removed through surgery.
The way the benign brain tumor would kill you is that the brain tumor would grow and grow and grow until the brain could not tolerate the large brain tumor.
That growing benign brain tumor can put pressure on your brain which could then rupture other parts of your brain which can then lead to death overtime.
It may take a few years before it got to the point of it growing enough to kill you but if you do have a benign brain tumor you should probably have it removed through surgery.
Or you could wait until it gets bigger and then have it removed.
Having brain surgery to remove any tumors is a serious surgery so you would want to think hard about having the surgery to remove the brain tumor.
But eventually the benign brain tumor could kill you so I would probably have it removed through surgery since the surgery is safer when the brain tumor hasn't gotten too big.