I Haven't Had A Period In Almost A Year. I

I haven't had a period in almost a year. I am 50 years old and have been peri menopausal for 12 years. Over the past 3 years I have experienced very few period, but some very heavy and clotted periods. By the time I had not had a period for 8 months we did an ultrasound, CT and the Dr tried to perform and Endometrial biopsy but couldn't because of a thickened lining. I had several fibroids. I went back for a second ultrasound after 11 months (3 months later) and had only 2 small ones. My question is at what point will the lining become thin again? Should this concern me?