I'm not in LE, but I carried a weapon daily while in the military, and was often placed in situations where using it was potentially possible.
Few, if any, LEO's fire thier weapons "in action" often enough to damage their hearing.
In fact, to use hearing protection while "on the job" could get you killed. In a combat situation, you need ALL of your senses... sight & hearing being the top 2 senses used in a deadly force situauion.
However, I HIGHLY recommend that hearing protection be used when at the range or during ANY extended practice/shooting session. I DON'T recommend using the bulky, slip on "head phone" type of hearing protection - its unrealistic for training for "real-life" situations. Instead I recommend the "in the ear" hearing protection like foam, etc...
Also, when I AM firing my weapon during training sessions, I usually don't hear my gun fire anyway... I'm too focused.
Stand against evil, lest evil have its way...