Interesting thread as always with this sort of discussion - just catching up.
To go back to the OP Morwenna - Taz is right that the reason many women decide to cut down or stop is because of the long-standing and unfortunately entrenched view amongst many of the medical profession that it is likely to be risky to continue post 60. In fact this view is outdated and based on the long study publushed 10-12 years ago - and which was found to be based on flawed evidence and was in any case only using HRT in the form of conjugated equine oestrogens ( Premarin etc) and a synthetic progestogen. Latest studies are showing increasingly that the type and mode of delivery of HRT can affect the risk - so that transdermal oestrogen (patch or gel) and micronised progesterone of the same molecular structure as we produce in our own bodies - will reduce the risk.
Dr Currie on this site considers that although the risks do probably increase post 60, between the ages of 60 and 70 the benefits of HRT equal the risk, and only beyond 70 do the risks start to outweigh the benefits.
http://www.menopausematters.co.uk/balance.php Of course this is a broad-brush view but a good rule of thumb.
I have always taken the same dose of oestrogen since I was late peri-menopause at almost 54, ie 50 mcg patch. Possibly I could have increased it and would benefit from this, but as Dana says many of us are limited in scope due to the progestogen. For me I have traded off increasing my dose for having a longer cycle. I would be too nervous to have both (by increasing oestrogen) because at 61 I don't want a big bleed - even if it is only every two months.
Also as we get older many of us begin to get abnormalities like fibroids which can grow with oestrogen (I have a small one - at least I hope it's still small!) which also makes one a bit more cautious as you get older.
In terms of osteoporosis prevention, whilst even a small amount of oestrogen can decreases bone loss to some extent ( ie will have some benefits), the only dose licensed to help prevent osteoporosis is a 50 mcg patch or greater.
Hurdity x
