what's relevant is how loud some signal will be for your ear. I don't know if we can increase the pressure and output by 50dB thanks to compressing the air inside the ear canal, but obviously when we do we notice how much louder it is. +10dB feels about twice as loud already, so +50dB isn't the kind of stuff that would ever stay unnoticed.
for any headphone or IEM you adjust the loudness yourself so who cares about how sensitive or how different acoustic situations could increase the output when fed with the same amp. it's irrelevant as you obviously set the loudness to whatever you feel comfy with.
what is relevant is how loud and how long you spend listening to music. quiet listening, regular pauses with as much silence as possible, will give you no reason to fear anything. but loud is dangerous it always will be and the longer you listen loud the worst the effect.
aside from those captain obvious generalizations of mine, if you insert and take out the IEM like a barbarian, it's clearly not good. another issue I've encountered is that an IEM may have a signature where you feel like it's not loud overall, but maybe there is that one spike that ends up 10 or 15dB louder and can in the long run damage the cells for that frequency. most people here have experienced IEMs they found rapidly tiring, and even some that did increase their tinnitus. I've had a few like that myself.
the last issue is simply about having a foreign object in your ear canal. some people really can't stand that, and a few have some reaction to the physical pressure, or how the ear stays humid and hot.
about the RE600, the obvious thing I can think about is how it doesn't isolate well, so if you're in a noisy environment, you probably naturally push the volume up so the music will cover that noise. and that's how we usually end up doing dumb stuff for our ears. try to be self conscious about the volume settings you're using, maybe test that at home in silence to decide what is pretty loud. and force yourself not to go over that limit when you're in a noisy environment. and if you need to go louder to enjoy or simply hear the music, then give up and get yourself something that isolates better, or wear earplugs when you're at those very noisy places.
in any case, I'm back as captain obvious, but if you notice a direct link between using your IEMs and ringing or other issues, I'd say: stop using the IEM.
