Speakers tend to reduce the duration of words that they have heard or spoken recently. We examine the cognitive mechanisms behind duration variation, focusing on the contributions of speaker-internal constraints and audience design. In three experiments, we asked speakers to give instructions to listeners about how to move objects. In Experiment 1, the instruction was preceded by an auditory prime, which elicited reduced spoken word duration on a target noun in a speakerprivilege condition, and additional reduction on a determiner in a mutual-knowledge condition. In Experiments 2a and 2b, we tested the related hypothesis that the speaker's experience articulating the target leads to fluent processing above and beyond fluency in other processing, such as lexical selection. While prior articulation of the target led to greater reduction than just thinking about the word (Experiment 2a), saying the prime led to equal reduction as hearing the prime (Experiment 2b). The pattern of results leads to the conclusion that facilitated processing, perhaps brought on primarily as a function of having heard a word, is a major contributor to durational reduction in running speech. While audience design also has a small effect, its effect may also be mediated by processing fluency.