I like the fingerprint metaphor, but fingerprints do not change. I remember a time when the spouse would do just about anything except public sex. Women have a temporal component to their sexuality which can change significantly when they are out of their prime child-bearing years. Men don't. I bet many of you know (or are) seniors who can fuck multiple times a day. Our appetite and libido just don't change much until we are much, much older, ill, or dying.