It was shown that the reverse-carpooling based network coding can improve the efficiency of multi-hop wireless networks. However, when no opportunity for coding exists at a relay node, should it transmit an uncoded packet or wait for the next opportunity to create a coded packet? While to wait for the next coding opportunity reduces the number of transmissions, it incurs packet delay. Two setting are considered: i.i.d. arrivals and adversarial arrivals. For the stochastic arrivals, we develop the optimal control that balance between costs of transmission against those of delays. We show that the stationary threshold type policy based on queue lengths is optimal. Moreover, for the arrivals controlled by adversary, we present an online algorithm that achieves the competitive ratio e/(e-1).