Together Longer With Others
The surprising association between relationship length and non-monogamy.
Posted May 31, 2026 | Reviewed by Tyler Woods
People sometimes wonder if having a non-monogamous sexual agreement is bad for a relationship. There are lots of ways to respond to that concern, and not all indicators will come to the same conclusions. One very straightforward observation about relationship length and sexual agreements suggests we should be skeptical about the inherent dangers of non- monogamy .
Couples who have been together longer are more likely to have non-monogamous agreements.
This positive association between relationship quality and the likelihood of being in a non-monogamous sexual agreement was first noted in studies of sexual minority men more than 20 years ago (LaSala, 2004). In more recent studies, non-monogamous couples were together on average 8.75 years longer than those couples with monogamous sexual agreements (Starks et al., 2019). Comparable studies of transgender women and men show a similar pattern.
Several factors may contribute to this correlation between relationship length and non-monogamy. LaSala (2005) found evidence suggesting that non-monogamous couples separated sex from emotional intimacy . Non-monogamy was about seeking sexual variety but did not present a threat to the unique emotional closeness of their primary relationship. Separately, Hoff and Beougher (2010) found that couples generally viewed the formation of a sexual agreement, even a non-monogamous one, as a demonstration of love and trust in their partner.
In short, it is possible that as couples are together longer the desire for variety or boredom follows and opening up their sexual agreement is one way to address that. It is also possible that as partners become more committed to one another over time it is easier for them to navigate the challenges of a non-monogamous sexual agreement.
It is also true that as relationships go on longer, the partners in that relationship are simultaneously getting older. There is some qualitative evidence suggesting that younger sexual minority men place more emphasis on monogamy as an indicator of commitment, particularly early in a relationship’s development (Dellucci et al., 2025).
Whatever the cause, this positive correlation between non-monogamy and relationship length should give us some assurance that non-monogamy can be a feature of a stable and enduring relationship. If non-monogamy was typically followed by relationship dissolution, we would expect those in relationships longer to have monogamous agreements – the opposite pattern from what we see. Open relationships not only can be long, many studies suggest they are more likely to be.
For more information on sexual agreements and related communication challenges , see my previous posts!
Dellucci, T. V., Lovejoy, T. I., Cain, D., Feldstein Ewing, S. W., Adhemar, C., Kyre, K. D., Outlaw, A. Y., Naar, S., & Starks, T. J. (2025). A narrative study of sexual agreements and HIV prevention strategies among emergind adult sexual minority men. Prevention Science , 26 (3), 462–472. https://doi.org/https://doi.org/10.1007/s11121-025-01789-9
Hoff, C. C., & Beougher, S. C. (2010). Sexual agreements among gay male couples. Archives of Sexual Behavior , 39 (3), 774–787. https://doi.org/10.1007/s10508-008-9393-2
LaSala, M. C. (2004). Extradyadic sex and gay male couples: Comparing monogamous and nonmogamous relationships. Families in Society; The Journal of Contemporary Social Services , 85 (3), 405–412.
LaSala, M. C. (2005). Monogamy of the heart: Extradyadic sex and gay male couples. Journal of Gay and Lesbian Social Services , 17 (3), 1–24. https://doi.org/https://doi.org/10.1300/J041v17n03_01
Starks, T. J., Robles, G., Bosco, S. C., Dellucci, T. V., Grov, C., & Parsons, J. T. (2019). The prevalence and correlates of sexual arrangements in a national cohort of HIV-negative gay and bisexual men in the United States. Archives of Sexual Behavior , 48 (1), 369–382. https://doi.org/10.1007/s10508-018-1282-8
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Tyrel Starks, Ph.D., is a Professor of Psychology at Hunter College of The City University of New York.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.