  We numerically study the radiative properties of the reverberation phase of
pulsar wind nebulae. Reverberation brings a significant evolution in a short
period of time. We show that even the Crab nebula, associated to the more
energetic pulsar of the sample we consider, has a period in its future time
evolution where the X-ray luminosity will exceed the spin-down power at the
time. In fact, all nebulae in our sample are expected to have a period of
radio, X-ray, and GeV superefficiency, and most will also have a period of TeV
superefficiency. We analyze and characterize these superefficient phases.
