This chapter challenges the idea that infrastructure maturity would be a phase of urban and infrastructural stability. In an increasing number of countries, mainly but not restrictively in the global North, the combination of infrastructure’s ageing and degradation, budgetary constraints and rising environmental issues has gradually shifted professional and public concerns from extension to repair and upkeep. This heralds what the authors coin an ‘age of infrastructure maintenance’, which dramatically contrasts with the modern infrastructural ideal. Drawing from the analysis of French water networks maintenance and asset management practices, this chapter investigates what this age of maintenance concretely encompasses, highlighting two main challenges a maintenance-centred and maturity-focused perspective raises for utilities, namely practices of knowledge production and forms of infrastructures valuation.