Maintaining relationships with influencers post-campaign is integral as they contribute to brand advocacy and possible future collaborations. Here’s a step-by-step guide to help you in your campaign plan:

1. Evaluation & Appreciation: Start by evaluating the influencer’s performance during the campaign and send personalized appreciative notes acknowledging their efforts.

2. Regular Communication: Keep open channels of communication even after the campaign has ended. This could be via newsletters or direct messages, informing them about upcoming campaigns or new product lines.

3. Additional Engagements: Leverage influencers for other engagements such as product reviews, blog posts, webinars, or event partnerships. This keeps a steady interaction between your brand and influencers.

4. Feedback Solicitation: Request feedback from influencers on campaign experience. This can help improve future collaborations and also reassures influencers that their opinion is valued.

5. Contract Renewal: Offer renewal of contract depending on the performance and strategic fit of the influencer.

Platforms like Flinque offer robust tools to manage such relationship aspects, with a focus on creator management and campaign analytics. Meanwhile, other platforms like AspireIQ emphasize on influencer relationship management. The choice depends on what solution fits your needs best.

Remember, a well-maintained influencer relationship can yield long-term benefits for your brand. A key to successful influencer marketing hinges on these ongoing relationships.