Do your DJs spill Pitchers of mixed drinks and beer in those? lol. I have Three main rules for my DJ booths, 1. No Drinks in the DJ Booth*, 2. Stay out of the "Red", 3. No Entourages aloud. (4.This is not coat check- for one of my smaller places that doesn't have a coat check). Now you since you can't expect these guys not to drink, I enforce rule number one very Leniently. I don't mind a drink or two but your working so don't get shit faced and if you are to have a drink, keep it on the ledge/drink rail behind you and away from the equipment! I also implemented a penalty system because accidents do happen, -If you spill a drink on/in any of the equipment tell me and we will split the repair cost. Now if you don't tell me and I find out it was you, then you will be responsible for the entire cost of repair. This works because every DJ that works is on the payroll for that night and i can track them down, usually the mixer will be "gunked up" within 24 hours or before the next time its used, where ill get a complaint from the following DJ that some of the equipment is messed up. Another reason why and how this works is that the repair is deducted from they're pay (so I'm not chasing people for money) and if they don't want to pay they don't play for me again.
Anyway more so on topic, I can't tell you how many CDJ's and mixers I have sent out for repair due to abuse (missing knobs, bad pots, stiff faders) and spills between the four bars over the past couple years before I implemented the penalty system. I can tell you that the 57 is a pretty resilient mixer though and it takes its fair share of abuse (I'm open with DJs from Tues-Sat every week). I can also tell you that the amount of repairs and dropped significantly since I have implemented the penalty system! FYI usual repair cost for a "Gunked up" 57 runs between $250 and $500 (though mostly towards $250) and "spilled on" CDJs usually run me about $200 a pop to fix. So IMO its not bad at all considering the amount the equipment is used to the cost it is repair/how much it originally cost and how much it is making.