Most second language acquisition (SLA) research has documented the processes involved in learning second/foreign languages, with few studies focusing on the durability of attained second language (L2) skills once instructed learners/users are no longer receiving formal instruction. The current study examines the effects of continued exposure and peak instructional attainment on the long-term evolution of advanced, instructed L2 learners' skills following a longitudinal mixed-methods research design. Participants (n = 28) completed an oral proficiency test, an oral interview, and a vocabulary knowledge test at multiple times over an 8-year period, 6 years of which were postinstruction. Results showed that continued exposure contributes to long-term retention (and some further development) of oral proficiency and fluency and that peak attainment at the end of formal instruction is also an important variable for some areas of L2 performance. Additionally, even the participants with limited exposure demonstrated little attrition over time.