can bipolar go away with age?

this is so weird but my grandma got diagnosed with bipolar 1 when she was sixteen, had psychotic episodes for a majority of her life, developed DID, was hospitalized multiple times, etc. and now, in her old age, she has absolutely no symptoms of any of these illnesses. she’s a happy, seemingly stable old lady, and when i asked her if she’s just medicated or what, she said she’s not medicated for it and that it just went away with age. is this possible?! do we have any older bipolar peeps who could speak on the progression/regression of their symptoms?