The present paper attempts to answer the question "is it worth implementing dynamic resource allocation in a metropolitan network ?". Our study evaluates the gain (CAPEX and OPEX) to expect in a Time-Domain Wavelength Interleaved Network (TWIN) when the number of active Tx/Rx changes, over the day, according to the traffic matrix. We assume that TWIN is implemented in an SDN framework in which burst emission schedules can be periodically recomputed thus taking into account traffic matrix changes. A comparative study is carried out to assess, for different values of the computation period, the OPEX and CAPEX savings on the basis of the number of active Tx/Rx. Results show that such a dynamic network reconfiguration approach can bring some CAPEX savings and more significant OPEX savings in a realistic metropolitan network scenario, even for rather large configuration periods.