As an OMB entertainer, I can assure you that the vast majority of us, those that do this for a living every day of the week, every week of the year, are very conscious of our volume levels, and never crank up to ear bleed dbs of 85, not even during a wild, outdoor party. Of course, it's not really necessary if you use high quality sound systems that provide equal distribution of sound throughout the venue, such as the Bose L1 and L1 Compact systems, which I've used for many years.
Some of the older bands, those using conventional sound systems, consisting of a powered mixer and huge, heavy speakers mounted upon poles, are hampered by range and falloff problems, which is why many top sound system manufacturers are following the lead of Bose. With a conventional sound system, the speakers are usually placed to the side and forward of the band members to prevent feedback. Small, wedge shaped monitor speakers positioned on the floor in front of the band and facing toward them, are often employed so the band can hear themselves playing without generating feedback. The problem with conventional speakers is the falloff amounts to 50 percent at a forward distance of 100 feet, which is horrendous. To offset this, the bands used to crank up the volume to ear bleed levels so the patrons at the back ends of the venues could hear them at dance levels, while those poor individuals seated near the stage were getting their heads blown off.
Bose solved this problem with the introduction of their vertical array system that widened the coverage area fro 45 degrees to 210 degrees. Additionally, the falloff at 100 feet is less than 10 percent, which means if the volume is acceptable to those in the front row of the audience, those in the back row can hear it equally as well. No conventional sound system does this. Additionally, the clarity of the Bose systems is beyond belief. No distortion whatsoever from overdriving the sound system, which has a limiter that prevents over driving. This is good news for good musician/singers, and bad news for those that are only marginal in those categories. If you make a mistake, or your vocals are not up to snuff, everyone in the audience will immediately know it if you are using the Bose systems.
One last note. For those using the Bose systems, ear buds are no longer necessary. That's because you hear exactly what the audience hears, and at the same volumes. Because of their technological advances in feedback rejection, the Bose sound system is placed behind the band, and a off to the sides - not in front. Lots of things have drastically changed in the wonderful world of OMB entertainers, and I am happy to say I was there to enjoy it to the fullest.
This is my current setup, using a single Bose L1 Compact, Yamaha arranger keyboard, headset mic (designed by Garth Brooks), a system that easily covers an audience of 150 people without cranking the master volume beyond the 10-O'clock position.
This is my older system, which employed a pair of monster, powered speakers of 1,000-watts that was hard pressed to cover audiences of more than 100 people.
All the best,