I work around jet engines, so like Bullseye, I am concerned for my future hearing so I always wear muffs at work and while shooting.
When I was shooting my MK II yesterday with Federal Bulk Packed Ammo, I thought the shots sounded like quiet, hollow thumps. So I took off my muffs and fired one shot. While it wasn't ear ringingly loud, I believe it was loud enough to effect my hearing over time.
While I don't personally believe that .22 ammo is loud enough to require doubling up, I know that Bullseye shoots .45 for sure, and who knows what else. And with the louder guns I wouldn't be surprised if doubling up your hearing protection would be beneficial. And if you wear double when you shoot one type of ammo, it wouldn't be a bad practice to get into the same habbit with all types of ammo.
And if I thought Bullseye, or anyone else for that matter, was "overprotecting" his hearing, I certainly wouldn't try to talk him out of it. You certainly can't argue with his results. With his decades of hearing loss free life, maybe he is on to something?