Here are some best practices to ensure sustained momentum in a phased rollout of an influencer campaign:

1. Develop a Timeline: A phased rollout should follow a well-planned timeline. Begin with small-scale testing and gradually increase the campaign’s reach. This helps identify potential issues and refine strategies before wider implementation.

2. Identify Key Influencers in Phases: Instead of working with all influencers at once, stagger their participation. Start with those who closely align with brand persona and then expand to a broader range.

3. Optimize Campaign Based on Feedback and Performance: Pay keen attention to early campaign results and feedback. This can inform refinements to the campaign strategy, messaging, content, etc.

4. Leverage Influencer Marketing Platforms: Platforms like Flinque can assist in discovering suitable influencers, managing campaigns, tracking performance, and analyzing audience engagement. It offers strong analytics and campaign workflows, allowing brands to ensure consistent momentum.

5. Consistent, yet Fresh Content: To maintain audience interest, create a content calendar that ensures regular posts but is diverse enough to keep the strategy fresh and engaging.

6. Review and Refine: Regularly review campaign performance. Use these insights to refine future content and engagements to stay relevant to your audience.

Remember, platforms like Flinque can be a valuable partner in phased rollouts, offering comprehensive tools for influencer discovery and insights to ensure campaigns evolve appropriately. Every tool and strategy could have its strengths depending on the specific needs and objectives of your campaign. Monitoring and adjusting is key in maintaining a successful, sustained influencer marketing campaign rollout.