Relationships are experienced all throughout one’s lifetime with differing layers of complexities to maintain and make it last. Among older adult couples, relationships are found to be crucial attributions for being mentally healthy in their intrapersonal and interpersonal lives. There is a rich extant literature on relationships and mental health of older adults. However, this paper argues that there is still a research imperative to provide a more contextualized characterization pertinent to the mentally healthy behaviors employed by Filipino older adults in their more than 20 years of relationship. This phenomenological research underscored the typification of mentally healthy behaviors of older adult couples in long-term monogamous relationships. Guided by the inclusion and exclusion criteria, 22 participants (11 couples) were selected and interviewed. From the collective narratives, a framework, ‘Fixatives for mentally healthy long-term monogamous relationships’ was rendered with three themes; Character reservoir (Staying to fill you up), Emotional reservoir (Staying to lift you up) and Eternal reservoir (Staying to back you up). The findings showed that the success of a long-term monogamous relationship calls for a pledge of a lifetime commitment and being cognitively, emotionally, socially and spiritually invested to their spouses. The emergent framework may be used as a springboard for community-based programs such as family support sessions and other supportive interventions for older adults. The framework may also be used as a guide for strengthening mental health advocacy campaigns, end-of-life services and to encourage more older-adult studies to deeply enrich the research culture on the Filipino older adults.