I second everything Rosa said. Perimenopause is an individual experience as our menstrual cycles and fertility.
I was in my early 40s when I began to enter perimenopause. I thought that I would be through it and over it by my mid-40s, such as my mother did. But, as it turned out, I was 54 before I reached actual menopause.
I don't know why it took so long for me.....yes, if you calculated, that would be 14 years before I actually stopped getting my periods. But, that is not a universal standard for all woman-kind.
In fact, the actual experience of perimenopause varies in intensity for many women. Some women literally slide through it, others, not so much.
It depends on the person and a variety of other factors as well.