Debates around age effects in L2 learning have mostly centred around the domains of phonology, morphosyntax, and lexis. In this chapter, we expand the scope to conceptual and cognitive restructuring, much in line with Long’s (1990, 2013) discussion of the limits of age effects. Drawing on an extensive review of the extant literature, the current chapter examines the role that age of L2 acquisition plays for phenomena of thinking-for-speaking and linguistic relativity. The chapter closes with methodological suggestions for future research.