@TheOGCCL The medical advice is that most women can switch to continuous progesterone by 54. By that age the vast majority of women are not having regular / any periods.
Obviously, if you are using HRT that gives a bleed, you can't tell.
You can either experiment and come off the HRT (but you'd need at least 3 months and more like 6 to see if you still had regular periods.) OR you can switch sooner than 54.
The only drawback is that ALL continuous HRT usually takes some time to settle - spotting is expected for up to 6 months.
If you are not post menopausal, then the dose of progesterone in a daily dose is often not enough to control the womb lining and you may still get (unexpected) natural periods.
One thing that is never mentioned, is that swapping to continuous is not mandatory. It's there mainly as a choice as most women do not want a bleed. It does mean that the risk of hyperplasia (thick womb lining) is reduced.
BUT (again, not mentioned) sequential HRT has a slightly lower risk of breast cancer. This is shown is the small print of the research. This is because the breasts are not being stimulated by 2 hormones every day. The sequential regime allows them a 'break' and it's also thought that it's progestogens that increase the risk of BC (when used alongside estrogen.)
This is why women using only estrogen HRT (they have no womb) have a very low risk of BC- lower than women NOT using HRT.