Periods become erratic during peri menopause. You may still get them but they could be further apart, or worse, more frequent as time goes on. Or for some lucky women they will just stop altogether. Being on HRT does not mean your periods won't stop. You are classed as being post menopausal once you haven't had a period in a year (if over 50) or 2 years (if under 50). You could go 9 months without one and then they could start up again. Its a real rollercoaster!