Filled pauses are widely considered as a relatively consistent feature of an individual's speech. However, acoustic consistency has only been observed within single-session recordings. By comparing filled pauses in two recordings made >2.5 years apart, this study investigates within-speaker consistency of the vowels in the filled pauses uh and um, in both first language (L1) Dutch and second language (L2) English, produced by student speakers who are known to converge in other speech features. Results show that despite minor within-speaker differences between languages, the spectral characteristics of filled pauses in L1 and L2 remained stable over time.