Not a DJ myself, but I've worked at a bar where we had DJ before and after live concerts. I have no clue about equipment, but I know that you're able to take breaks as long as you have songs lined up. Depending on the equipment that means you can put on 2-3 songs and bugger off for ten minutes, but any breaks longer than what you need to smoke a cigarette, pee and buy another beer is frowned upon (and doing all three at the same time is really stretching it).
DJs always get the most flack, and I'm saying this as an ex-bouncer! Sure I got some drunk moron quarrelling with me for fifteen minutes ("I'm not that drunk!" "Yes you are." "How do you know?" "You were asleep on the floor." "I got sleepy!" "You were sleeping in your own vomit."), but they had the morons who wanted them to put on [insert popular pop song / ancient rock ballad here], turn up the volume, change their whole playlist... People even managed to complain about the metal songs being played before and after a metal band played (it's too noisy! This band isn't metal enough! This band is death metal, but the music is black metal! It's not black enough!). They kept complaining about it even after the DJ put on the band's newest CD and buggered off.
A legend in our bar is the tale of a DJ who finally had enough. He was told to put on [pop song X] by a couple of annoying girls. First he told them he didn't want to. When that didn't work, he claimed he didn't have the CD. They pointed the CD out on the shelf behind him, where they are lined up, and he pulled it out, opened the cover, broke the CD, showed them the pieces and calmly said "Like I said, I don't have the CD."
Another time one of our DJs was thrown out of the club for playing music the owner didn't like (indie rock at a rock bar). She went and started a club concept at another bar, which "stole" a lot of our clientèle the years she kept it going. This was the source of whole lot of drama between the management and the ground floor workers (bar, security, DJ), as we were all on the DJs side.
Another kernel of drama is when you have more than on DJ that night (mostly only on club nights, aka. no live music, only DJing), and they can't agree on the last song of the night. At least for our DJs, the last song of the night is something special. The one time I remember one of the DJs wanted to play "Je Ne Regrette Rien" and the other one wanted to play "Time Warp". The Edit Pjaf lover won the stone-paper-scissor contest, and went around bragging while we all cleaned up for the day that the whole room had sung with him, and even started leaving on their own accord when the song was over. This caused the other DJ to claim they were escaping the music, and the only one singing was DJ A. The bar crew actually had to declare a winner before we could leave that night (Edit Pjaf won).
At our bar, the DJ staff are the only ones allowed to drink at the job, which means the rest of the ground floor crew usually don't like them very much. They rub it in people's faces. This can fall back on themselves if they get too drunk, though, as we're allowed to thrown them out for drunkenness just like a regular client. In those cases we find a mix CD to put on and call in a replacement.
The punishment for spilling beer on the equipment is buying new equipment, which no DJs working for the kind of pay they got where I worked could afford, so most DJs stay sober enough to avoid drunken accidents. Accidental destruction of property while sober is not punished, but the moment you've had more than one beer everything you break is put on your tab.