Anecdotal evidence is that Western women often go into sexual libido decline after four or five years of a relationship, which is something they may not emerge from for a lifetime. There have been countless studies on this, with some interesting results. Women who are married to a partner who is better educated and / or earns a lot of money tend not to suffer libido decline. It was felt by researchers that these women keep the supply of sex up to keep other women away from a man they regard as a 'good catch'.
My own relationship is with an African woman, and her libido was high when we first met, and has never faltered over almost a quarter-century. Culturally, Africans are very 'into' sex, so this is probably the reason why she is the way she is. Culturally, Christian influence is asexual, which is the converse of the rest of the world! Anecdotally, Asian women have the reputation of high levels of lifetime sexual desire as well. Budhism encourages good sex.
One thing I do know is that women who partially abstain from sex (say after the birth of a baby) suffer a loss of testosterone, which lowers libido, which probably means less sex, with a further of lowering of testosterone, and so on. The converse is true: have sex with your husband, new baby or not, and your sex drive will remain high and healthy. Also, for a bit of effort, your husband will think you're the most wonderful wife in the world too (sex is exceptional for relationship-bonding).
Off the track: I was a bit under the weather yesterday, with a sore throat from hayfever, a minor headache and my ever-present pain from my right leg (the result of minor spinal column nerve damage). My wife and I had sex, which is the way we celebrate the end of the working week, and after my sore throat was all but gone, my headache was gone, and the pain in my leg was barely noticeable! My wife has told me that she has sometimes initated sex when she's been feeling a bit second-hand, because she knows that it will make her feel better.
