That's just it, trying to predict when bleeding will occur in late perimenopause is like trying to time the stock market.
If your bleed pattern has been regular on sequential up until now this suggests you are probably just having withdrawal bleeds, which can be induced in 80 year olds by giving them sequential.
This is actually how combined HRT was designed, and it was intended for postmenopausal women only back in the 70s so of course the artificial withdrawal bleeding on it was regular.
After it became apparent that whilst this prevented endometrial cancer Vs using estrogen alone, it had high discontinuation rates as women didn't want their periods back - shame nobody had asked in the product development phase.
So continuous combined was developed, but then nobody knew what to do with all these fixed dose sequential products that had cost a fortune to develop and market, plus perimenopause was starting to be recognised, so someone thought I know, let's give the sequential to all these perimenopausal women, assuming that because it induced regular bleeds postmenopausally, it would do so in peri.
This was not based on any science it was an economic solution to salvage an unpopular product, and as a look round this site will tell you, chaotic and unpredictable bleeding with so much angst over what day to start progesterone is rife.