I'm 56 and still have regular monthly cycles every 29 days. My gyn says according to my hormone blood work I am post-menopausal. I asked her how could I still be having periods and she said "I dunno."
She did a trans-vaginal ultrasound and said I was ok except uterine lining was a little thick, nothing emergency level but she did recommend a complete hysterectomy and to use a bhrt pellet afterward. Regardless, I still have normal monthly cycles. I have never gone a year without a period. About 4 years ago I skipped my period off and on for about a year. Then they returned and have gone every month since. Not sure what's going on but I suppose I will have the surgery. My Mom did this when she was my age and her gyn told her that she was still ovulating from one ovary. Maybe that's what I'm doing but I have just started having hot flashes after starting to take prometrium for the uterine lining issue. My gyn says it has about a 1% chance of turning malignant and that's enough reason to take it out and ovaries should come out too since they are just sitting there waiting to get cancer in the future or so gyn says.