In this paper, we study an archetypal formulation that captures the key timing trade-off of network expansion decisions.On the one hand, building an arc early on implies a high fixed cost, but the arc can be used to route commodities for alarge number of subsequent periods. On the other hand, building an arc later in the horizon is associated with a lower fixedcost, but the number of periods in which the arc can be used is smaller. The objective is then to jointly minimize the arcconstruction and operating costs over the given planning horizon.