Long-term, monogamous, relationships are often portrayed as protective in HIV prevention campaigns. Focusing on marriage in a community in south west Uganda, we examine why and how people enter long term relationships, what their expectations are and what factors sustain those relationships. Qualitative data were collected using in-depth interviews with 50 men and women randomly selected from a General Population Cohort. The results showed that managing expectations to sustain marriage is challenging; however the socio-economic and cultural benefits of marriage: having children, property acquisition as well as securing societal status tend to overshadow the costs associated with risks from infidelity such as sexually transmitted infections (including HIV). Recognising the compromises that couples may make to sustain their marriage is an important step towards acknowledging that 'being faithful' may be about staying together and showing commitment, not sexual exclusivity.