We investigate the roles that efficiency and effectiveness play in speakers’ repetition of shared word sequences, or constructions, in task-oriented dialogue. We find that repeating constructions has negative effects on information rate and positive effects on rate of delivery, that information rate managing strategies are predictive of task success, and that this varies by the communicative function of the constructions being repeated. More effective dialogue is characterised by greater levels of shared construction usage and more efficient task-related repetition; while task-agnostic repetition can seem redundant, it can serve important efficiency and effectiveness functions. Our results provide a nuanced picture of the importance of repetition and of developing a shared lexicon for both efficiency and effectiveness in task-oriented dialogue.