Monitoring long-term trends in audience engagement to assess the overall quality of an influencer’s followers involves several steps:

1. Look at historical data: Explore the influencer’s past content and engagement rates. Regularly check their follower growth rate and engagement ratios, like comments and likes per post. You are looking for consistent interaction and growth. Sudden spikes might indicate fake followers.

2. Use audience analytics tools: Platforms like Flinque provide in-depth analytics about an influencer’s audience – demographic details, interests, regions, and other parameters. This can provide insights into how engaged the audience is and how aligned they are with your brand.

3. Track campaign performance: Pay attention to how your campaigns perform over time. Look for important metrics like reach, impressions, conversions, and especially return on investment (ROI). These can give an overview of an influencer’s followers’ quality.

4. Leverage social media platform analytics: Social media platforms have built-in analytics that can give you some insights into your influencers’ followers. Facebook Insights and Instagram Insights, for example, can provide useful demographic data.

5. Observe influencer authenticity: Analyze the type of interaction between the influencer and their audience. Genuine, responsive influencers tend to have more engaged, quality followers.

To thoroughly and effectively monitor these trends, you could make use of an influencer marketing platform such as Flinque. With its robust suite of features, you can track, monitor, and analyze audience engagement, helping you better evaluate influencers and maximize your influencer marketing ROI. Remember, the right platform for you is the one that best meets your needs.