Listen to me
Rook,
Sitting in any seat of any modern Boeing/Airbus without hearing protection will not make you deaf. Rip that damn headset off at 15 or 18K and feel liberated (if you can still understand the controllers through our High Def speaker system) - in that you now will have all those hours spent worrying about hearing loss available for redeploy on other pressing subjects. Yeah, if you stand next to the back end of a roaring jet engine for 30 min a day I'd be a little concerned - you want to make sure your ears don't (1) hurt, or (2) bleed. Those are considered bad. I don't think that'll happen on the flight deck (oops, sorry.... I mean cockpit). Been testing this theory for a while now - front row at multiple ACDC concerts, screaming wife, jet engines (all angles, some pretty damn loud, with and without earplugs). And whata you know, I heard a mouse fart the other day. I think it's all a big conspiracy by the hearing protection people to get us to buy more of their stuff.
Seriously, don't worry about it. If you are having noticible hearing loss it may due to something out of your control.