The seven-year-itch refers to the notion that dissatisfaction arises in a relationship around the seven-year mark. While limited research specifically addresses its validity, it is believed to possibly correlate with when partners have fully gotten to know each other, and the novelty and excitement of discovery wane. Looking at divorce rates and other behavioral patterns, there seems to be some merit to the idea, though it’s more about how couples perceive and handle this transitional phase rather than the itch itself.
  

Key Points: 

1. The seven-year-itch is the supposed feeling of restlessness or dissatisfaction in a relationship after about seven years.
2. Neurochemicals like dopamine, linked to the excitement of new love, dissipate over the first few years but can linger as couples continue to discover nuances about each other.
3. Data suggests that, on average, the highest risk of divorce occurs 5-8 years into a marriage, which, accounting for dating time, aligns somewhat with the concept of the seven-year-itch.
4. The seven-year-itch isn’t strictly negative but signals a transition in a relationship; past this phase, risk of divorce decreases notably.
5. The diminishing of relationship excitement over time is replaced by feelings of stability, security, and profound intimacy, suggesting couples can navigate past this phase for richer experiences.

Source: https://www.artofmanliness.com/people/relationships/is-the-7-year-itch-real/