I agree with Powertool45...........once you start shooting you will no doubt end up with diminished hearing capability probably somewhat comparable to wearing hearing protection anyway, so why don't you "play it by ear" (he he he...no pun intended) and use the hearing protection in practical situations.
A practical situation may be one where there is some open space between you and the threat in which your sight is number one. Another may be one in which there is such a high rate of noise anyway that your hearing is diminished due to things other than your hearing protection, i.e.........factories, alarms of some sort, explosions or surrounding gunfire, etc. So why not simply use your hearing protection and save your hearing as much as possible?
Now I also thought of something that I haven't seen anyone else mention and that's what I call the buck fever effect. You hunters know what I mean. When your adrenaline kicks in and you don't even realize you have heard a particular very loud noise and your hearing is not affected. Your brain isn't concentrating on it and therefore ignores the effects somewhat. For example, you have a shot at a trophy animal, raise your rifle, take aim, press the trigger and the animal is down. You are so excited that you don't even realize the shot was that loud and your hearing is certainly not affected in the sense that you have any diminished hearing. Maybe on a medical scale you might, but not for practical purposes. You carry on with the day with no after effects at all.
Could this idea also take place when you are firing or under fire? Or would you become somewhat desensitized to the buck fever effect and end up having your hearing affected? Just some things to think about. I for one will be taking earplugs with me and I use them in all PRACTICAL situations on a case by case basis but as much as possible. There is nothing I hate more than having to suffer the after effects of a gunshot or two without earplugs. I don't want to imagine having to live for extended periods of time that way. And if you ended up that way, does it not reduce your overall tactical effectiveness? I think so.