Despite a significant decline in HIV transmission in Australia, many people living with HIV continue to face stigma and discrimination. For gay men, historically at high risk for HIV, peer support programs are essential to improve psychosocial outcomes. Peer support is known to reduce stigma demonstrably, improve well-being, increase medication adherence, and connect participants to broader HIV services. While peer support is known to be important within the HIV care continuum, there is little research on factors associated with engagement with peer support and no Australian study has examined determinants of involvement. This study focused on Australian gay men living with HIV for at least five years to understand the factors impacting engagement, retention, and attrition. Twenty participants with 5-36 years of lived experience participated in semi-structured interviews. Reflexive thematic analysis revealed four key themes: (1) shared experiences, (2) confidentiality and trust, (3) changing needs with aging, and (4) inclusion and collaboration. The themes highlight the importance of fostering connection, trust, program adaptability, and agency. Barriers to engagement included problems with online support access due to cost, limited technological proficiency, and concerns about program relevance for aging men who have extensive HIV lived experience. The findings underscore the need for consistent funding to support well-defined program scopes that cater to diverse and changing needs. Such enhanced program support is crucial to address the specific requirements of men with long-term experience of living with HIV as they age through the HIV care continuum.