Inventor collaborations that span across regions facilitate the combination and diffusion of innovation-related knowledge. While remote partnerships are gaining importance; most R&D cooperations remain embedded in local environments and little is known about how spatial patterns of creation and persistence of ties in large-scale co-inventor networks differ. We use the publicly available OECD REGPAT database to construct a co-inventor network of the EU27 and continental EFTA countries from patents filed between 2006 and 2010, and identify those ties that had been persisted from before 2006. A community detection exercise reveals that persisted collaborations cluster at a smaller geographical scale than what is observed in the full network. We find that in general the estimated probability of persisted collaboration does not differ from the complete collaboration network when geographical distance, technological similarity or the number of common third partners across regions are assumed to influence tie probability separately. However, persistent collaboration gains exceptional likelihood if regions are proximate in all three dimensions. Our results therefore offer evidence that repeated inventor collaboration drives regional innovation systems towards isolation, which is a threat for European innovation policy.