In bootcamp my SDI was a stinger gunner. It cost something like 60k for him to "practice" firing, including the cost of the drone. He was a SSGT, had been in for 11 years at the time I knew him, and he'd actually fired the weapon once. There was another gunner there training at the same time, so two people fired at the same drone.

We can train everyone without this level of exposure, and I can imagine a world where your dose is tracked like radiation, kept to a safe level, and people are forced into retirement after they hit the limit.