The FIDELIS TDR Network brings together digital repositories committed to the trustworthy, long-term stewardship of research data. Soft-launched in April 2025 with 72 provisional members, the Network now faces a critical transition: FIDELIS project funding concludes in December 2027[1], and the Network must become self-sustaining beyond that point. The central challenge is converting provisional members into committed, fee-paying members. This requires addressing concerns around perceived value, senior management buy-in, financial constraints, and competition from other networks and membership bodies. The strategy responds to this challenge through three mutually reinforcing objectives: crystallising a compelling membership value proposition; embedding members in governance and Network activities; and testing and stabilising a sustainable financing model. Together, these aim to transform the Network from a project-delivered offering into a member-run organisation with durable relevance and impact. Concrete actions to deliver this include producing a Network charter, developing an independent brand and online presence, establishing a governance committee and general assembly, delivering training and capacity-building activities, and agreeing stewardship arrangements for key shared outputs. A sustainability plan and host arrangement for the Secretariat will be finalised ahead of the Network's hard-launch in Q4 2027, at which point membership fees will be introduced. A fourteen-point roadmap tracks these activities from Q4 2025 through to December 2027, with two General Assemblies serving as key decision-making milestones. The strategy will be updated in 2027 to reflect progress and emerging priorities. [1] https://eden-fidelis.eu (funded via EU Horizon Europe HORIZON-INFRA-2024-EOSC-01-03; Grant agreement ID: 101188078)