seven-year itch
noun [ S ] informal humorous uk/ˌsev.ən.jɪə ˈrɪtʃ/ us/ˌsev.ən.jɪr ˈrɪtʃ/
(婚姻的)七年之痒
A married person who has the seven-year itch is feeling unhappy with their marriage after seven years, and is considering having a sexual relationship with another person.