This may be a result of several things. The first is the Control Panel being run on constantly run on high levels. Only raise the Control Panel when needed and lower it when not needed. The will preserve the life of the probe and make sure you don’t overdose the copper. The second reason is the conductivity of the water. Water with higher conductivity will exhaust the probe faster. For example, adding salt to the pond will super charge the probe and cause it to exhaust faster. If you notice you probe exhausting quickly you can operate the ionization system at a lower rate. Possibly conduct a water change if salt was used in order to reduce conductivity.