I remember an article in the NYTimes a few years ago about HRT and the responses came pouring in mainly from women of course. So many of them said I'm in my 70 or 80s and they still have hot flashes, so I guess it lasts forever !!
I keep my fan out year round and at night I open the window a bit, two minutes later I cool down and shut it, three minutes later I open the window, get up three minutes later and shut it again , three minutes later open the window again . . . . . .