It goes away when you’re not into ketosis anymore. There are no mints or amount of brushing that will fix it because it comes from your lungs, it’s the acetone that’s a byproduct of ketosis that you exhale.
Also, this question is better suited to /r/keto
Depends largely on the person. After years…I still get it and carry keto friendly mints. It cones and fmgies for me…but is still around. Same as the metallic thing…still get that. I think for most it subsides as they become fat adapted (general assumption on that part)