I feel like these studies are a bit suspect. The first one had fewer than 30 people of each gender surveyed - that's too small a sample size to trust the results.

In the second study the only people surveyed were undergraduate students - people whose sexual habits and relationship style are not the same as those of fully mature adults in actual long term relationships. After all - to an 18 year old, their longest relationship is at most a couple of years, but more likely a few months. Compare to someone who's been married 20 years. What a very young person considers "relationship satisfaction" and what an older adult defines as such, is also unknown. As such you can't necessarily generalise these results to the whole population. Especially since younger people have different expectations around "hookups" than older people.

I am also confused about the "sexual desire decreasing by 0.02" thing. 0.02 of what? Are you saying by 2%? According to this research by 50 months, a woman's sexual desire will be at 0. But that's not the case in most relationships.