This article explores knowledge outcomes of international researcher mobility in the social sciences and humanities. Looking in particular at international experiences of longer durations in the careers of European PhD graduates, it proposes a threefold analytical typology for understanding the links between the modes, durations, and outcomes of this mobility in terms of the exchange of codified knowledge; the sharing of more tacit knowledge practices; and the development of a cosmopolitan identity. The findings suggest that, under the right conditions, there can be an important and transformative value to longer stays, which can lead to enduring outcomes in terms of knowledge production and innovation and the spatially distributed networks that sustain it.