This paper explores issues that come up in practices of breakage and repair through two projects: the 'XO' laptops of One Laptop Per Child in Paraguay and public sites of facilitated repair in California, USA. Collectively drawing on 15 months of ethnographic fieldwork, 156 interviews, and archival research, we find that breakdown and repair are not processes that designers can effectively script ahead of time; instead, they emerge in everyday practice. These practices are shaped by material, infrastructural, gendered, political, and socioeconomic factors -- such as manufacturing limitations, access to repair parts and expertise, and environmental convictions -- which designers often did not, and may not have been able to, anticipate. We call the material realities and practices of repair negotiated endurance, which is illustrated by four themes from our findings: the negotiated identification of breakdown, collaborative definitions of worth, the fraught nature of collaborative expertise, and the gendered stakes of repair.