Usually every 2nd or 3rd time I change the batter heads I will change the resos. Typically the same for the snare, but I replace snare heads more frequently so this happens at a faster rate.
This isn't a must though. As long as the drums still sound as good as they should, tune up well and stay in tune, then it isn't exactly a necessity. We drummers, especially gearhead drummers like myself, often get wrapped up in various aspects of our equipment, but in reality, all that matters is the sound.