I think it is slowly becoming accepted that ages of menopause do not always fit the text books, both in early and late meno.
In my experience 51 seems reasonable to still be peri. I am almost 57, which is quite unusual it seems. And get pms and sometimes spotting ( am on mirena so no real periods) every 4 weeks without fail. No sign of finishing or even becoming erratic. My sister was 58 and had erratic periods before finally becoming post meno.
It is hard not to compare with other women and their own experiences. I get very frustrated \ angry that most of my friends had all finished by 50! But like Taz, I don't think you are behind the curve. It's gotta stop sometime, but that doesn't help us still going through it. Watch your iron levels maybe if the flooding continues.?
Take care x