The present study investigated which factors would best predict second-language (L2) fluency in a group of long-term L2 speakers of different English varieties with German as their first language.

L2 fluency was conceptualized in terms of utterance fluency for which speed, breakdown and repair fluency were distinguished.

Multiple measures of utterance fluency were applied to four-minute speech fragments originating from 102 spontaneous oral interviews. Interviewees’ ages of onset ranged from 7 to 17, whereas their ages at interview ranged from 57 to 87. Multifactorial analyses yielded significant effects of age at interview.

Whereas the mean number of silent pauses and repairs increases, syllable duration decreases. This leaves room for interpretation as to why we find an aging effect. Overall, the evidence suggests that the usual, L2 acquisition-specific factors, such as age of onset or length of residence, are no longer at play to predict L2 fluency.

To this point L2 fluency in very advanced, highly proficient L2 speakers has received little attention. The results point to the need for more research into highly proficient L2 users.