When running sound off stage it is a good idea to walk around a bit and hear the mix from different parts of the room. This is especially important when an audience is in front of the PA, and you are behind the audience. The human body has the tendency to absorb many frequencies. Therefore you may be kicking up the highs from your position and killing the people in the front row. This will reveal clipping or distortion you might not have heard otherwise I dicovered one of my horns clipping to the point of coming on and off,using this method.
Some speakers have internal speaker protection which uses a small light-bulb to absorb peak wattage.
This can be a very scary thing to discover at a show. I once had a singer run out of the room screaming when he saw his monitor light up. Never set drinks anywhere where they can easily spill onto your soundboard or any other essential equipment. Spills are almost inevitable, and whether it's beer, milk, or even water, it can do heavy and expensive damage to your stuff once it gets inside. Also, I can attest from personal experience that cat urine can cause you to have to make an expensive trip to the repair shop.