We're quite partial to our ears here at Blue Cow as they pretty much keep us in business. A new Australian study has shown some worrying results regarding hearing loss and headphones. The study shows 60% of those who regularly listen to music through
headphones play it loud enough to damage their ears. More Here
It's something I've been emphasising when teaching: "sound engineers who damage their ears will have very short careers". You can substitute "sound engineer" with "musician", "radio journalist", "film editor" and so on, but it doesn't rhyme as well.
If you're using headphones a lot invest in a good closed ear design that blocks out more of the ambient noise. This means the music doesn't need to turned up as high to hear the details. If you must use in-ear headphones then consider spending a bit more to get something like the Shure Sound Isolating Headphones. These are basically earplugs with speakers in them.I have a pair of the older Shure E-3's which are amazing in terms of quality and isolation.