As chakra increases with age in youth , I can only assume that it would also start reducing in old age.Gradually her reserves would decrease. She would die. She may even die faster as she is using chakra for looks. However, she could die looking young if she chooses to do so.
Not that i dislike her but it would have been better if she died in the war then went off with Dan and Nawaki. Then it should have been kakashi at the ex kage meeting. And it would make more sense why she suddenly stepped down and then let kakashi be hokage for less than 10 years for him to quit aswell.