Hi menomummy, I'm one of those in the 15% Hurdity mentioned who currently doesn't get a bleed on sequi HRT. I'm now 7+ years postmenopause, had BSO approx 2 years ago & on a low dose regimen with only 25mcg oestrogen patch, so likely any lining build-up is being effectively thinned by the low dose progestogen.
Ironically, in earlier postmenopause, I bled intermittently throughout my 2+ years on "no-bleed" Evorel Conti & had to have several scans & eventually a hysteroscopy with biopsy as a result. That just showed an atrophied uterus & the bleeding was thought to be a consequence. Measurement of oestradiol later showed poor absorption from the Evorel.
If your symptoms are well controlled on the Evorel Sequi so that you want to stick with it, you could have an endometrial scan to see what's going on. I intend to do this as although I enjoy the lack of bleeds, I'm uneasy not knowing for sure what's going on. As I'm still getting menopause symptoms, poor absorption, or the 25mcg Estradot simply being too low a dose could explain this & the absence of bleeds! If your symptoms are not well controlled on the Evorel Sequi, poor absorption could perhaps be the reason for your lack of bleeds.
P.S. You were posting while I was writing this without knowing the bigger picture! Hope there's still something helpful in it.