We estimate and compare the effect of increased time costs on consumer satisfaction and behavior. We are able to move beyond the existing literature, which focuses on satisfaction and intention, and estimate the effect of waiting time on return behavior. Further, we do so in a prosocial context and our measure of cost is the length of time a blood donor spends waiting. We find that relying on satisfaction data masks important time cost sensitivities; namely, it is not how the donor feels about the wait time that matters for return behavior, but rather the actual duration of the wait. Consistent with theory we develop, our results indicate that waiting has a significant longer-term social cost: we estimate that a 38% increase (equivalent to one standard deviation) in the average wait would result in a 10% decrease in donations per year.