As all the other posters have said, look after your hearing - you can only lose it once!
Exposure to loud noise, eg the disco, causes hearing loss at the higher frequencies first. Fortunately, the hearing test requirements want you to be able to hear at the lower frequencies, ie the frequencies relating to normal speech. Hearing loss at the higher frequencies is not a problem for the class 1.
My hearing is appalling at the higher frequencies and has been commented on at every renewal. I have never spent any time in discos and put it down to the effects of gunfire (another story).
So, hearing loss, per se, is not the problem. It is whether it is at the higher frequencies, or the lower.
Whatever, I invested in an ANR headset. Worth every penny I would say.