Repeated exposure to Subject Island violations can lead to increased acceptability ratings and faster reading times (Chaves & Dery, 2014, 2019; Clausen, 2011; Francom, 2009; Hiramatsu, 2000; Lu et al. 2021; Lu et al., 2022). However, it remains unclear what the nature of this effect and the driving mechanism is. The present paper describes a longitudinal investigation to test whether the effect of repeated exposure to Subject Island constructions is short-lived or whether it can spread over three weeks’ time, as measured by offline measures (Likert acceptability ratings) and online measures (self-paced reading). Using more observations and more sensitive methodologies, our work builds and improves on the only previous longitudinal study on such islands, Snyder (2022). We uncover evidence suggestive of gradual and strategic (by-construction and by-region) adaptation to Subject Island violations, indicated by faster response times, as well as higher acceptability ratings following repeated exposure, most consistent with a syntactic adaptation effect over and above task adaptation.