IEM's are most certainly touted as a hearing saver! By having the sound directed into the ear canal and a proper fit blocking out all other sound, IEM's are designed to give you what you need at a reasonable volume. This is why a careful eye must be kept on the volume, and using the units limiter is always recommended.
One thing that really hurts the IEM/Ear saver is people who use just one IEM... This actually causes more trouble than just a loud monitor, since it will also cause the brain to try to compensate for the differences in volumes in each ear and can be a very nasty problem. Performers may experience more fatigue at the end of the night, and will most certainly have caused more damage to the exposed ear as a result.
Just like anything in the musical equipment world, there will be people who use them incorrectly and ultimately cause damage with them, but In-ear bud manufacturers are doing the best they can to provide great noise reduction and clean sound so you don't have to crank them up.
I have been more and more impressed with the selection of kid-friendly headphones at the NAMM show. Each year more products are released that will sound good and not go to damaging levels. Now if we could only get parents to pay more attention and stop kids from cranking up the volume...
Maybe this is what I've been hearing about. No pun intended.
But truly, cranking up the volume on a good Bassman or Super Lead is an experience that has to be felt, not just heard. I just don't recommend doing it often or close in.
Seriously, I did work with a bass player who vibrated our hollow platform. Then I understood, I had the insight, the revelation, the tao-chi-whatever-you-call-it of why people like lots of bass. Actually, I had it the first time I played an organ with full reeds, mixtures and a two 32' pedal stops below.
And, yes, don't do it all the time, or nothing else will satisfy you, and you'll blow everyone out of the house.
Depending on your needs Rolls makes a nice little wired 6 channel headphone amp/mixer, so each person can have their own mix with 6 things in it. As stated not everyone really needs wireless, just maybe the singers who may be better served with better wedges, wider dispersion. With everyone else on wired In ears.
Also the idea of taping the cables of guitars/bass to a cable with a jack for the Headphones sounds like a good one.
Depending on needs, the HearBack system is actually a pretty good deal, too. It's a wired in ear solution that gives performers a mix of up to '8' things. It is not totally ideal for 8, since two things will be sharing a stereo channel (and panned to the Left or Right because of it), but a church I played in for over a year used them and it was a great solution. There are much better units around, but the cost also indicates how much better the manufacturer thinks they are....
One aspect of this matter of monitors, and sound level in general, is that human ears become inured (jaded, used to) to sound level. If we are interested in a sound, we want to come closer to hear it. In general, we find ourselves creeping up the level. The level that was fine in rehearsal seems inadequate when the youth pastor comes out and starts the service "DO YOU LOVE HIM DO YOU LOVE JESUS ARE YOU READY TO PRAIIIIIIIIISE HIM WORSHIP TEAM LET'S GO!" And you've got this nice opener all set to 85 dB.
What do you do? You tweak everything up 10%, and by the time the set is over, 30%.
And the live experience -- who among us has not ripped those headphones off so we could actually BE there?
A couple of extra mics facing the congregation. That stopped me from having to take the buds out, ever. Once we started running ambient mics and could hear the congregation singing back to us, I never felt the need to pull them out.
I also value my hearing in a big, big way (not to say that you guys don't as well..). I have made money with my ears (playing, working in live sound, etc...) since I was 17. I do what I can to ensure that I will be able to continue using my ears without abusing them. I also love finishing a gig with my band and being able to go to sleep with no ringing in my ears. Best. Feeling. Ever!