Hi Spangles,
the withdrawal bleed on HRT will likely continue as long as you take it. Mine stays mostly constant starting on the end of the progesterone phase, but sometimes it can start as late as day 7/8 of the estrogen, but only once a year ish, mostly on the first couple of days into the estrogen.
Most ladies have gone into actual menopause and the periods have stopped by 54, but that is the average.
I too am loathed to try any other form of HRT at the moment, though mine is far from ideal. I could not take the risk of increasing anxiety, let alone the physical symptoms which would leave me unable to work. Once I get to the 55/56 mark I will consider changing and going transdermal, maybe with a longer estrogen cycle if I can, as by then I hope that I will be post meno.
Peppermintyx