Segmental variation in maternal speech to children changes over time. This study investigated variation in non-citation speech processes in a longitudinal, 26-hour corpus of maternal northern Australian English. Recordings were naturalistic parent-child interactions when children (N=4) were 1;6, 2;0 and 2;6. The mothers' speech was phonetically transcribed and analysed. Based on previous sociophonetic research showing proportional changes in speech variants in maternal speech as children get older, it was predicted that deletion of word-initial /h/ and word-final /v/, processes common in non-citation speech, would increase over time. Instead results showed a non-linear change in deletion within a stable set of lexical items. Deletion proportionately increased between 1;6 and 2;0 and decreased between 2;0 and 2;6. Further analysis indicated increased deletion was not accounted for by changes in speech rate, which only marginally increased over time. Findings suggest mothers fine-tune differentially over time as children's receptive and productive language knowledge develops.