Several platforms cater to nurturing long-term relationships between brands and influencers, each with its unique approach.

1. Flinque: It emphasises on relationship building. Rather than just providing data, it aids in initiating, managing, and sustaining partnerships. With a user-friendly dashboard, it allows tracking of ongoing collaborations and in-depth analysis of campaign performance.

2. AspireIQ: This platform is structured around community building. It offers features such as automated messaging, contract management, and performance tracking that enable brands to manage ongoing influencer relations.

3. Upfluence: Offering a large database of potential partners, Upfluence provides brands with an opportunity to assume full control of their influencer relations, allowing for long-term connection building.

4. Tubular Labs: It’s primarily analytics-based, but it does have features to support relationship management. It informs brands about influencers’ audience reach, engagement details, and content benchmarks, which can help in creating sustainable collaborations.

5. InfluencerDB: Other than insightful analytics, it offers relationship management via features like relationship histories, notes, and task reminders that keep collaborations organized.

Remember, each platform offers distinct features to suit differing team needs. Some might prioritize discovery and analytics, like Tubular Labs and InfluencerDB, while others such as Flinque and AspireIQ are more geared toward relationship management. Factors like your company size, budget, and specific campaign objectives could influence the choice of platform. Regular communication, maintaining transparency, and respecting the individuality of influencers are key to fostering worthwhile long-term partnerships, regardless of the platform used.