This research explores the sustainability of marriage, understood as long-term unions with high marital quality, by analyzing the styles of marital relationships in Switzerland. Using longitudinal representative data from the survey 'Social stratification, cohesion and conflict in contemporary families', we analyzed a subsample of 343 couples (1,029 observations) across three waves over 20 years. Cluster analysis identified five styles of marital relationship: Companionship, Bastion, Cocoon, Parallel and Association, based on several dimensions of family life. These styles were then linked to indicators of marital quality-marital satisfaction, relationship problems, and thoughts of separation, using multilevel mixed-effects regression models. Results show that couples who belong to the Companionship style, characterized by mutual commitment, external openness, and gender equality, report significantly higher marital quality. The Companionship style becomes more prevalent over time, as couples who initially developed Cocoon and Bastion styles (Institutional marriage) gradually switch to this style. In contrast, Association and Parallel styles (Individualistic marriage) remain relatively stable over time and are consistently associated with lower marital quality. These findings highlight the importance of relational dynamics within couples in maintaining sustainable marriages and demonstrate the predictive value of marital relationships over time.