I am not trying to play the wise person here - but just my humble opinion. Our ears will acclimate to higher listening levels quickly (just like the nose to strong odors). However, turning up the volume at this stage can lead to deleterious long term effects on hearing. Also, one of the problems being that the deterioration in hearing sensitivity is slow to progress and hence goes unnoticed until it is too late.
The contrary works too - if you listen at low levels, your ears will after some time, automatically adjust to the new sound level (provided your hearing is not already compromised).
One thumb rule to test hearing is to gently rub your thumb and index finger against each other, keeping level with the ear and from about 3-4 inches away. If you can hear the sounds, you are probably OK. If you cannot hear it at all, then you might want to get your hearing levels checked and stop listening to loud music. Also, before performing this, ear wax from the canal should be cleaned out.
HTH,
akart.