Gamification has been widely used to increase learners' motivation and engagement in digital learning environments. Various studies have highlighted the need to tailor gamification according to users' characteristics. However, little is known about how tailoring gamification affects learners' engagement when interacting with the environment. In this paper, we analyse learners' behaviours in a large-scale field study in real-world classroom conditions over a six-week period. We identify three behavioural patterns and show at a global level that two of these patterns are influenced by adaptation. When we look at how learners' engagement evolves over time, we see more differences in the adapted condition, specifically in the final lessons of the experiment. Globally learners' engaged behaviours gradually decreased over time but tailoring the game elements to learners seemed to reduce this decrease or make it more stable, depending on the behavioural patterns.