> I'm just curious about this thing I keep hearing from different sources
> that claims that women have increased sex drive as they get to their mid
> to late 30s? True for most or just some women?
Yes, that's true for a lot of women.
The reason's fairly obvious. As women get older, their estrogen levels begin to drop as the ovaries age. Women also produce testosterone, some from the ovaries (which doesn't really decline with age) and some from the adrenals.
As women age, therefore, their hormonal balance shifts from being estrogen-dominated towards a balance which favours testosterone rather more.
Basically, the less feminine a woman is, the greater her sex drive.
You can, of course, find the same, and higher, levels of sex drive in some younger women. Sadly, most guys seem to rather avoid those of us who do have that sort of drive at a younger age.
It's not even difficult to spot women with high a sex drive. The randiest women are those who show most evidence of a high testosterone to estrogen ratio.
The physical signs of that are limited breast development and a tendency to "male" pattern hair growth (moustache etc.).