The notion of advance planning of sentence intonation is grounded in the positive correlation between the sentence-initial intonation peaks and sentence duration. This study examined real-time sentence planning and intonation using visual world speech production. In two eye-tracking experiments, native Estonian speakers described transitive events involving multiple actors. Conceptual complexity of the resulting picture descriptions was manipulated through a pictorial design, while sentence length was controlled for by manipulating specific task characteristics. In Experiment I, conceptual complexity of the picture descriptions varied together with linguistic complexity, while linguistic complexity was held constant in Experiment II. As the conceptual complexity of utterances increased, the duration of naming gazes also increased, indicating less incremental conceptual planning. Notably, while utterance-initial intonation peaks did not correlate with the relative duration of naming gazes, they were influenced by utterance length. These findings highlight advance planning of intonation in Estonian. Furthermore, they suggest that intonation planning depends on linguistic information that is rapidly activated after establishing a comprehensive conceptual framework during earliest stages of preverbal planning.