My father-in-law is a Korean War vet, and he was exposed to gunfire and artillery, sustained and repeated for hours at a time. He finally needed a hearing aid at age 62, 40 years after the war. His hearing loss is no worse than many men his age.
I have an uncle who fought in Vietnam, including extensive time manning an M-60 machine gun. He is now approaching 70 years, and no hearing aid yet.
Hearing loss due to gunfire is real. Tinnitus is real. We all should protect our hearing while training and hunting, all the time, no exception. But exposure to gunfire does not automatically lead to hearing loss. It may in some circumstances, but it often does not. Many people have been exposed to a single very loud concussion (indoor gunfire, explosion, etc), and have suffered only a temporary hearing loss, with no permanent damage.